diff --git a/src/aleph/db/accessors/messages.py b/src/aleph/db/accessors/messages.py
index dc1c351ea..08be2a457 100644
--- a/src/aleph/db/accessors/messages.py
+++ b/src/aleph/db/accessors/messages.py
@@ -4,7 +4,7 @@
 
 from aleph_message.models import ItemHash, Chain, MessageType
 from sqlalchemy import func, select, update, text, delete, nullsfirst, nullslast
-from sqlalchemy.dialects.postgresql import insert
+from sqlalchemy.dialects.postgresql import insert, array
 from sqlalchemy.orm import selectinload, load_only
 from sqlalchemy.sql import Insert, Select
 from sqlalchemy.sql.elements import literal
@@ -105,7 +105,7 @@ def make_matching_messages_query(
         )
     if tags:
         select_stmt = select_stmt.where(
-            MessageDb.content["content"]["tags"].contains(tags)
+            MessageDb.content["content"]["tags"].has_any(array(tags))
         )
     if channels:
         select_stmt = select_stmt.where(MessageDb.channel.in_(channels))
diff --git a/src/aleph/db/accessors/posts.py b/src/aleph/db/accessors/posts.py
index 2f8fc6f3d..50a1e72d4 100644
--- a/src/aleph/db/accessors/posts.py
+++ b/src/aleph/db/accessors/posts.py
@@ -28,7 +28,7 @@
     Float,
     case,
 )
-from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.dialects.postgresql import JSONB, array
 from sqlalchemy.orm import aliased
 from sqlalchemy.sql import Select
 
@@ -230,7 +230,7 @@ def filter_post_select_stmt(
         select_stmt = select_stmt.where(literal_column("original_type").in_(post_types))
     if tags:
         select_stmt = select_stmt.where(
-            literal_column("content", type_=JSONB)["tags"].astext.in_(tags)
+            literal_column("content", type_=JSONB)["tags"].has_any(array(tags))
         )
     if channels:
         select_stmt = select_stmt.where(literal_column("channel").in_(channels))
diff --git a/tests/api/conftest.py b/tests/api/conftest.py
index 151596cc3..10a4ffa12 100644
--- a/tests/api/conftest.py
+++ b/tests/api/conftest.py
@@ -1,7 +1,8 @@
 import json
 from pathlib import Path
-from typing import Any, Dict, Sequence, cast
+from typing import Any, Dict, Sequence, cast, Tuple
 
+import pytest
 import pytest_asyncio
 from aleph_message.models import AggregateContent, PostContent
 from sqlalchemy import insert
@@ -10,12 +11,13 @@
 from aleph.db.models import (
     MessageDb,
     ChainTxDb,
-    AggregateElementDb, message_confirmations,
+    AggregateElementDb,
+    message_confirmations,
 )
 from aleph.db.models.posts import PostDb
 from aleph.toolkit.timestamp import timestamp_to_datetime
 from aleph.types.db_session import DbSessionFactory
-
+import datetime as dt
 
 # TODO: remove the raw parameter, it's just to avoid larger refactorings
 async def _load_fixtures(
@@ -122,3 +124,67 @@ async def fixture_posts(
         session.commit()
 
     return posts
+
+
+@pytest.fixture
+def post_with_refs_and_tags() -> Tuple[MessageDb, PostDb]:
+    message = MessageDb(
+        item_hash="1234",
+        sender="0xdeadbeef",
+        type="POST",
+        chain="ETH",
+        signature=None,
+        item_type="storage",
+        item_content=None,
+        content={"content": {"tags": ["original", "mainnet"], "swap": "this"}},
+        time=dt.datetime(2023, 5, 1, tzinfo=dt.timezone.utc),
+        channel=None,
+        size=254,
+    )
+
+    post = PostDb(
+        item_hash=message.item_hash,
+        owner=message.sender,
+        type=None,
+        ref="custom-ref",
+        amends=None,
+        channel=None,
+        content=message.content["content"],
+        creation_datetime=message.time,
+        latest_amend=None,
+    )
+
+    return message, post
+
+
+@pytest.fixture
+def amended_post_with_refs_and_tags(post_with_refs_and_tags: Tuple[MessageDb, PostDb]):
+    original_message, original_post = post_with_refs_and_tags
+
+    amend_message = MessageDb(
+        item_hash="5678",
+        sender="0xdeadbeef",
+        type="POST",
+        chain="ETH",
+        signature=None,
+        item_type="storage",
+        item_content=None,
+        content={"content": {"tags": ["amend", "mainnet"], "don't": "swap"}},
+        time=dt.datetime(2023, 5, 2, tzinfo=dt.timezone.utc),
+        channel=None,
+        size=277,
+    )
+
+    amend_post = PostDb(
+        item_hash=amend_message.item_hash,
+        owner=original_message.sender,
+        type="amend",
+        ref=original_message.item_hash,
+        amends=original_message.item_hash,
+        channel=None,
+        content=amend_message.content["content"],
+        creation_datetime=amend_message.time,
+        latest_amend=None,
+    )
+
+    return amend_message, amend_post
diff --git a/tests/api/test_list_messages.py b/tests/api/test_list_messages.py
index c317b38a9..d75877729 100644
--- a/tests/api/test_list_messages.py
+++ b/tests/api/test_list_messages.py
@@ -5,6 +5,8 @@
 import aiohttp
 import pytest
 
+from aleph.db.models import MessageDb, PostDb
+from aleph.types.db_session import DbSessionFactory
 from .utils import get_messages_by_keys
 
 MESSAGES_URI = "/api/v0/messages.json"
@@ -149,18 +151,74 @@ async def test_get_messages_multiple_hashes(fixture_messages, ccn_api_client):
 
 
 @pytest.mark.asyncio
-async def test_get_messages_filter_by_tags(fixture_messages, ccn_api_client):
+async def test_get_messages_filter_by_tags(
+    fixture_messages,
+    ccn_api_client,
+    session_factory: DbSessionFactory,
+    post_with_refs_and_tags: Tuple[MessageDb, PostDb],
+    amended_post_with_refs_and_tags: Tuple[MessageDb, PostDb]
+):
     """
     Tests getting messages by tags.
     There's no example in the fixtures, we just test that the endpoint returns a 200.
-    # TODO: add a POST message fixture with tags.
     """
 
-    tags = ["mainnet"]
+    message_db, _ = post_with_refs_and_tags
+    amend_message_db, _ = amended_post_with_refs_and_tags
 
-    response = await ccn_api_client.get(
-        MESSAGES_URI, params={"tags": ",".join(tags)}
-    )
+    with session_factory() as session:
+        session.add_all([message_db, amend_message_db])
+        session.commit()
+
+    # Matching tag for both messages
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "mainnet"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 2
+
+    # Matching tags for both messages
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "original,amend"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 2
+
+    # Matching the original tag
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "original"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 1
+    assert messages[0]["item_hash"] == message_db.item_hash
+
+    # Matching the amend tag
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "amend"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 1
+    assert messages[0]["item_hash"] == amend_message_db.item_hash
+
+    # No match
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "not-a-tag"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 0
+
+    # Matching the amend tag with other tags
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "amend,not-a-tag,not-a-tag-either"})
+    assert response.status == 200, await response.text()
+    messages = (await response.json())["messages"]
+    assert len(messages) == 1
+    assert messages[0]["item_hash"] == amend_message_db.item_hash
+
+
+@pytest.mark.asyncio
+async def test_get_messages_filter_by_tags_no_match(fixture_messages, ccn_api_client):
+    """
+    Tests getting messages by tags.
+    There's no example in the fixtures, we just test that the endpoint returns a 200.
+    """
+
+    # Matching tag
+    response = await ccn_api_client.get(MESSAGES_URI, params={"tags": "mainnet"})
     assert response.status == 200, await response.text()
     messages = (await response.json())["messages"]
     assert len(messages) == 0
diff --git a/tests/api/test_posts.py b/tests/api/test_posts.py
index bc25e7088..72bc8f5a2 100644
--- a/tests/api/test_posts.py
+++ b/tests/api/test_posts.py
@@ -5,8 +5,6 @@
 
 from aleph.db.models import MessageDb
 from aleph.db.models.posts import PostDb
-import datetime as dt
-
 from aleph.types.db_session import DbSessionFactory
 
 POSTS_URI = "/api/v1/posts.json"
@@ -55,70 +53,6 @@ async def test_get_posts(ccn_api_client, fixture_posts: Sequence[PostDb]):
     assert_posts_equal(posts, fixture_posts)
 
 
-@pytest.fixture
-def post_with_refs_and_tags() -> Tuple[MessageDb, PostDb]:
-    message = MessageDb(
-        item_hash="1234",
-        sender="0xdeadbeef",
-        type="POST",
-        chain="ETH",
-        signature=None,
-        item_type="storage",
-        item_content=None,
-        content={},
-        time=dt.datetime(2023, 5, 1, tzinfo=dt.timezone.utc),
-        channel=None,
-        size=254,
-    )
-
-    post = PostDb(
-        item_hash=message.item_hash,
-        owner=message.sender,
-        type=None,
-        ref="custom-ref",
-        amends=None,
-        channel=None,
-        content={"swap": "this"},
-        creation_datetime=message.time,
-        latest_amend=None,
-    )
-
-    return message, post
-
-
-@pytest.fixture
-def amended_post_with_refs_and_tags(post_with_refs_and_tags: Tuple[MessageDb, PostDb]):
-    original_message, original_post = post_with_refs_and_tags
-
-    amend_message = MessageDb(
-        item_hash="5678",
-        sender="0xdeadbeef",
-        type="POST",
-        chain="ETH",
-        signature=None,
-        item_type="storage",
-        item_content=None,
-        content={},
-        time=dt.datetime(2023, 5, 2, tzinfo=dt.timezone.utc),
-        channel=None,
-        size=277,
-    )
-
-    amend_post = PostDb(
-        item_hash=amend_message.item_hash,
-        owner=original_message.sender,
-        type="amend",
-        ref=original_message.item_hash,
-        amends=original_message.item_hash,
-        channel=None,
-        content={"don't": "swap"},
-        creation_datetime=amend_message.time,
-        latest_amend=None,
-    )
-
-    return amend_message, amend_post
-
-
 @pytest.mark.asyncio
 async def test_get_posts_refs(
     ccn_api_client,
@@ -233,3 +167,141 @@ async def test_get_amended_posts_refs(
     assert post["original_item_hash"] == original_post_db.item_hash
     assert post["ref"] == original_post_db.ref
     assert post["content"] == amend_post_db.content
+
+
+@pytest.mark.asyncio
+async def test_get_posts_tags(
+    ccn_api_client,
+    session_factory: DbSessionFactory,
+    fixture_posts: Sequence[PostDb],
+    post_with_refs_and_tags: Tuple[MessageDb, PostDb],
+):
+    message_db, post_db = post_with_refs_and_tags
+
+    with session_factory() as session:
+        session.add_all(fixture_posts)
+        session.add(message_db)
+        session.add(post_db)
+        session.commit()
+
+    # Match one tag
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": "mainnet"}
+    )
+    assert response.status == 200, await response.text()
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 1
+    assert response_json["pagination_total"] == 1
+
+    post = response_json["posts"][0]
+    assert post["item_hash"] == post_db.item_hash
+    assert post["original_item_hash"] == post_db.item_hash
+    assert post["content"] == post_db.content
+
+    # Unknown tag
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": "not-a-tag"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 0
+    assert response_json["pagination_total"] == 0
+
+    # Search for several tags
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": f"mainnet,not-a-ref"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 1
+    assert response_json["pagination_total"] == 1
+
+    post = response_json["posts"][0]
+    assert post["item_hash"] == post_db.item_hash
+    assert post["original_item_hash"] == post_db.item_hash
+    assert post["ref"] == post_db.ref
+    assert post["content"] == post_db.content
+
+    # Check for several matching tags
+    # Search for several tags
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": f"original,mainnet"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 1
+    assert response_json["pagination_total"] == 1
+
+    post = response_json["posts"][0]
+    assert post["item_hash"] == post_db.item_hash
+    assert post["original_item_hash"] == post_db.item_hash
+    assert post["ref"] == post_db.ref
+    assert post["content"] == post_db.content
+
+
+@pytest.mark.asyncio
+async def test_get_amended_posts_tags(
+    ccn_api_client,
+    session_factory: DbSessionFactory,
+    fixture_posts: Sequence[PostDb],
+    post_with_refs_and_tags: Tuple[MessageDb, PostDb],
+    amended_post_with_refs_and_tags: Tuple[MessageDb, PostDb],
+):
+    original_message_db, original_post_db = post_with_refs_and_tags
+    amend_message_db, amend_post_db = amended_post_with_refs_and_tags
+
+    original_post_db.latest_amend = amend_post_db.item_hash
+
+    with session_factory() as session:
+        session.add_all(fixture_posts)
+        session.add(original_message_db)
+        session.add(original_post_db)
+        session.add(amend_message_db)
+        session.add(amend_post_db)
+        session.commit()
+
+    # Match one tag
+    response = await ccn_api_client.get("/api/v0/posts.json", params={"tags": "amend"})
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 1
+    assert response_json["pagination_total"] == 1
+
+    post = response_json["posts"][0]
+    assert post["item_hash"] == amend_post_db.item_hash
+    assert post["original_item_hash"] == original_post_db.item_hash
+    assert post["ref"] == original_post_db.ref
+    assert post["content"] == amend_post_db.content
+
+    # Unknown tag
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": "not-a-tag"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 0
+    assert response_json["pagination_total"] == 0
+
+    # Tag of the original
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": "original"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 0
+    assert response_json["pagination_total"] == 0
+
+    # Search for several tags
+    response = await ccn_api_client.get(
+        "/api/v0/posts.json", params={"tags": "mainnet,not-a-tag"}
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json["posts"]) == 1
+    assert response_json["pagination_total"] == 1
+
+    post = response_json["posts"][0]
+    assert post["item_hash"] == amend_post_db.item_hash
+    assert post["original_item_hash"] == original_post_db.item_hash
+    assert post["ref"] == original_post_db.ref
+    assert post["content"] == amend_post_db.content