diff --git a/src/sentry/api/endpoints/organization_stats_v2.py b/src/sentry/api/endpoints/organization_stats_v2.py
index bc5b6771e455d7..9a355f4567e7ad 100644
--- a/src/sentry/api/endpoints/organization_stats_v2.py
+++ b/src/sentry/api/endpoints/organization_stats_v2.py
@@ -216,7 +216,7 @@ def build_outcomes_query(self, request: Request, organization):
         return QueryDefinition.from_query_dict(request.GET, params)
 
     def _get_projects_for_orgstats_query(self, request: Request, organization):
-        # look at the raw project_id filter passed in, if its empty
+        # look at the raw project_id filter passed in, if its -1
         # and project_id is not in groupBy filter, treat it as an
         # org wide query and don't pass project_id in to QueryDefinition
         req_proj_ids = self.get_requested_project_ids_unchecked(request)
@@ -229,11 +229,10 @@ def _get_projects_for_orgstats_query(self, request: Request, organization):
             return [p.id for p in projects]
 
     def _is_org_total_query(self, request: Request, project_ids):
-        return all(
-            [
-                not project_ids or project_ids == ALL_ACCESS_PROJECTS,
-                "project" not in request.GET.get("groupBy", []),
-            ]
+        # ALL_ACCESS_PROJECTS ({-1}) signals that stats should aggregate across
+        # all projects rather than filtering to specific project IDs
+        return project_ids == ALL_ACCESS_PROJECTS and "project" not in request.GET.get(
+            "groupBy", []
         )
 
     @contextmanager
diff --git a/static/app/views/organizationStats/index.spec.tsx b/static/app/views/organizationStats/index.spec.tsx
index 552076c9bfc6ba..e15ef611368bea 100644
--- a/static/app/views/organizationStats/index.spec.tsx
+++ b/static/app/views/organizationStats/index.spec.tsx
@@ -75,7 +75,15 @@ describe('OrganizationStats', () => {
    * Base + Error Handling
    */
   it('renders the base view', async () => {
-    render(<OrganizationStats />, {organization});
+    render(<OrganizationStats />, {
+      organization,
+      initialRouterConfig: {
+        location: {
+          pathname: '/organizations/org-slug/stats/',
+          query: {project: [ALL_ACCESS_PROJECTS.toString()]},
+        },
+      },
+    });
 
     expect(await screen.findByTestId('usage-stats-chart')).toBeInTheDocument();
 
@@ -245,6 +253,12 @@ describe('OrganizationStats', () => {
     OrganizationStore.onUpdate(newOrg, {replace: true});
     render(<OrganizationStats />, {
       organization: newOrg,
+      initialRouterConfig: {
+        location: {
+          pathname: '/organizations/org-slug/stats/',
+          query: {project: [ALL_ACCESS_PROJECTS.toString()]},
+        },
+      },
     });
 
     expect(await screen.findByText('All Projects')).toBeInTheDocument();
diff --git a/static/app/views/organizationStats/index.tsx b/static/app/views/organizationStats/index.tsx
index 8fc576789808cf..5fec9fca907849 100644
--- a/static/app/views/organizationStats/index.tsx
+++ b/static/app/views/organizationStats/index.tsx
@@ -19,7 +19,6 @@ import {normalizeDateTimeParams} from 'sentry/components/organizations/pageFilte
 import {ProjectPageFilter} from 'sentry/components/organizations/projectPageFilter';
 import SentryDocumentTitle from 'sentry/components/sentryDocumentTitle';
 import {DATA_CATEGORY_INFO, DEFAULT_STATS_PERIOD} from 'sentry/constants';
-import {ALL_ACCESS_PROJECTS} from 'sentry/constants/pageFilters';
 import {t, tct} from 'sentry/locale';
 import ConfigStore from 'sentry/stores/configStore';
 import {space} from 'sentry/styles/space';
@@ -167,10 +166,7 @@ export class OrganizationStatsInner extends Component<OrganizationStatsProps> {
 
   // Project selection from GlobalSelectionHeader
   get projectIds(): number[] {
-    const selection_projects = this.props.selection.projects.length
-      ? this.props.selection.projects
-      : [ALL_ACCESS_PROJECTS];
-    return selection_projects;
+    return this.props.selection.projects;
   }
 
   get isSingleProject(): boolean {
diff --git a/tests/snuba/api/endpoints/test_organization_stats_v2.py b/tests/snuba/api/endpoints/test_organization_stats_v2.py
index 9bf670cd9bf938..7f0da07fa095ad 100644
--- a/tests/snuba/api/endpoints/test_organization_stats_v2.py
+++ b/tests/snuba/api/endpoints/test_organization_stats_v2.py
@@ -33,12 +33,17 @@ def setUp(self) -> None:
         self.project3 = self.create_project(organization=self.org2)
 
         self.user2 = self.create_user(is_superuser=False)
+        self.user3 = self.create_user(is_superuser=False)
         self.create_member(user=self.user2, organization=self.organization, role="member", teams=[])
         self.create_member(user=self.user2, organization=self.org3, role="member", teams=[])
         self.project4 = self.create_project(
             name="users2sproj",
             teams=[self.create_team(organization=self.org, members=[self.user2])],
         )
+        self.project5 = self.create_project(
+            name="users3sproj",
+            teams=[self.create_team(organization=self.org, members=[self.user3])],
+        )
 
         self.store_outcomes(
             {
@@ -85,6 +90,18 @@ def setUp(self) -> None:
                 "quantity": 1,
             }
         )
+        self.store_outcomes(
+            {
+                "org_id": self.org.id,
+                "timestamp": self._now - timedelta(hours=1),
+                "project_id": self.project5.id,
+                "outcome": Outcome.ACCEPTED,
+                "reason": "none",
+                "category": DataCategory.ERROR,
+                "quantity": 1,
+            },
+            2,
+        )
 
         # Add profile_duration outcome data
         self.store_outcomes(
@@ -284,7 +301,7 @@ def test_timeseries_interval(self) -> None:
                 isoformat_z(floor_to_utc_day(self._now)),
             ],
             "groups": [
-                {"by": {}, "series": {"sum(quantity)": [0, 6]}, "totals": {"sum(quantity)": 6}}
+                {"by": {}, "series": {"sum(quantity)": [0, 8]}, "totals": {"sum(quantity)": 8}}
             ],
             "start": isoformat_z(floor_to_utc_day(self._now) - timedelta(days=1)),
             "end": isoformat_z(floor_to_utc_day(self._now) + timedelta(days=1)),
@@ -312,8 +329,8 @@ def test_timeseries_interval(self) -> None:
             "groups": [
                 {
                     "by": {},
-                    "series": {"sum(quantity)": [0, 0, 0, 6, 0]},
-                    "totals": {"sum(quantity)": 6},
+                    "series": {"sum(quantity)": [0, 0, 0, 8, 0]},
+                    "totals": {"sum(quantity)": 8},
                 }
             ],
             "start": isoformat_z(
@@ -344,7 +361,7 @@ def test_user_org_total_all_accessible(self) -> None:
                 isoformat_z(floor_to_utc_day(self._now)),
             ],
             "groups": [
-                {"by": {}, "series": {"sum(quantity)": [0, 7]}, "totals": {"sum(quantity)": 7}}
+                {"by": {}, "series": {"sum(quantity)": [0, 9]}, "totals": {"sum(quantity)": 9}}
             ],
         }
 
@@ -450,6 +467,10 @@ def test_open_membership_semantics(self) -> None:
                     "by": {"project": self.project2.id},
                     "totals": {"sum(quantity)": 1},
                 },
+                {
+                    "by": {"project": self.project5.id},
+                    "totals": {"sum(quantity)": 2},
+                },
             ],
         }
 
@@ -973,6 +994,118 @@ def test_profile_duration_groupby(self) -> None:
             ],
         }
 
+    @freeze_time(_now)
+    def test_project_filtering_with_all_projects(self) -> None:
+        """Test that project=-1 aggregates data across all projects in the org"""
+        response = self.do_request(
+            {
+                "project": [-1],
+                "statsPeriod": "1d",
+                "interval": "1d",
+                "field": ["sum(quantity)"],
+                "category": ["error", "transaction"],
+            },
+            status_code=200,
+        )
+
+        assert response.data["groups"] == [
+            {
+                "by": {},
+                "totals": {"sum(quantity)": 9},
+                "series": {"sum(quantity)": [0, 9]},
+            }
+        ]
+
+    @freeze_time(_now)
+    def test_project_filtering_without_project_param(self) -> None:
+        """Test that when no project parameter is provided, it filters by user's projects (my projects)"""
+        response = self.do_request(
+            {
+                "statsPeriod": "1d",
+                "interval": "1d",
+                "field": ["sum(quantity)"],
+                "category": ["error", "transaction"],
+            },
+            status_code=200,
+        )
+
+        assert response.data["groups"] == [
+            {
+                "by": {},
+                "totals": {"sum(quantity)": 7},
+                "series": {"sum(quantity)": [0, 7]},
+            }
+        ]
+
+    @freeze_time(_now)
+    def test_project_filtering_with_specific_project(self) -> None:
+        """Test that when a specific project id is provided, it filters by that project only"""
+        response = self.do_request(
+            {
+                "project": [self.project.id],
+                "statsPeriod": "1d",
+                "interval": "1d",
+                "field": ["sum(quantity)"],
+                "category": ["error", "transaction"],
+            },
+            status_code=200,
+        )
+
+        assert response.data["groups"] == [
+            {
+                "by": {},
+                "totals": {"sum(quantity)": 6},
+                "series": {"sum(quantity)": [0, 6]},
+            }
+        ]
+
+    @freeze_time(_now)
+    def test_project_filtering_with_multiple_specific_projects(self) -> None:
+        """Test filtering with multiple specific project IDs"""
+        response = self.do_request(
+            {
+                "project": [self.project.id, self.project2.id],
+                "statsPeriod": "1d",
+                "interval": "1d",
+                "field": ["sum(quantity)"],
+                "category": ["error", "transaction"],
+            },
+            status_code=200,
+        )
+
+        assert response.data["groups"] == [
+            {
+                "by": {},
+                "totals": {"sum(quantity)": 7},
+                "series": {"sum(quantity)": [0, 7]},
+            }
+        ]
+
+    @freeze_time(_now)
+    def test_with_groupby_project(self) -> None:
+        """Test that groupBy=project shows individual project stats"""
+        response = self.do_request(
+            {
+                "statsPeriod": "1d",
+                "interval": "1d",
+                "field": ["sum(quantity)"],
+                "category": ["error", "transaction"],
+                "groupBy": ["project"],
+            },
+            status_code=200,
+        )
+
+        assert response.data["groups"] == [
+            {
+                "by": {"project": self.project.id},
+                "totals": {"sum(quantity)": 6},
+            },
+            {
+                "by": {"project": self.project2.id},
+                "totals": {"sum(quantity)": 1},
+            },
+        ]
+
 
 def result_sorted(result):
     """sort the groups of the results array by the `by` object, ensuring a stable order"""