diff --git a/src/providers/postgres/qgspostgresprovider.cpp b/src/providers/postgres/qgspostgresprovider.cpp
index 4221cf8b5416..584a91dc6156 100644
--- a/src/providers/postgres/qgspostgresprovider.cpp
+++ b/src/providers/postgres/qgspostgresprovider.cpp
@@ -4609,13 +4609,15 @@ Qgis::VectorExportResult QgsPostgresProvider::createEmptyLayer( const QString &u
   {
     pkList = parseUriKey( primaryKey );
     const auto constPkList = pkList;
+    const bool lowercaseFieldNames = options && options->value( QStringLiteral( "lowercaseFieldNames" ), false ).toBool();
     for ( const QString &col : constPkList )
     {
       // search for the passed field
       QString type;
       for ( int fldIdx = 0; fldIdx < fields.count(); ++fldIdx )
       {
-        if ( fields[fldIdx].name() == col )
+        const QString fieldName = lowercaseFieldNames ? fields[fldIdx].name().toLower() : fields[fldIdx].name();
+        if ( fieldName == col )
         {
           // found, get the field type
           QgsField fld = fields[fldIdx];
diff --git a/tests/src/python/test_provider_postgres.py b/tests/src/python/test_provider_postgres.py
index 7d533159d79e..ac370084bb27 100644
--- a/tests/src/python/test_provider_postgres.py
+++ b/tests/src/python/test_provider_postgres.py
@@ -3266,6 +3266,50 @@ def testGeographyAddFeature(self):
         self.assertTrue(dp.addFeature(f))
         self.assertEqual(vl.featureCount(), 1)
 
+    # See: https://github.com/qgis/QGIS/issues/55856
+    def testPktLowerCase(self):
+        # check that primary key creation correctly works
+        # when exporting a vector layer to postgresql with
+        # lowercaseFieldNames option set to True
+
+        # create an empty vector layer
+        pk_key = "DEP"
+        input_uri = f"NoGeometry?crs=&field={pk_key}:string(255,0)&field=REG:string(255,0)&field=Number:integer(10,0)"
+        layer = QgsVectorLayer(input_uri, "lowercase", "memory")
+        self.assertTrue(layer.isValid())
+
+        # export the vector layer to postgresql with lowercase field names
+        self.execSQLCommand('DROP TABLE IF EXISTS qgis_test.pk_lowercase')
+        output_uri = f'{self.dbconn} table="qgis_test"."pk_lowercase" key=\'{pk_key.lower()}\''
+        err = QgsVectorLayerExporter.exportLayer(layer, output_uri, "postgres", layer.crs(), False, {'lowercaseFieldNames': True})
+        self.assertEqual(err[0], QgsVectorLayerExporter.ExportError.NoError,
+                         f'unexpected import error {err}')
+
+        # retrieve the columns and type and check them
+        cur = self.con.cursor()
+        sql_cols = (
+            "SELECT column_name, data_type FROM information_schema.columns "
+            "WHERE table_name = 'pk_lowercase' AND table_schema = 'qgis_test';"
+        )
+        cur.execute(sql_cols)
+        expected_cols = [
+            ('dep', 'character varying'),
+            ('reg', 'character varying'),
+            ('number', 'integer')]
+        self.assertEqual(cur.fetchall(), expected_cols)
+
+        # Retrieve the primary key and check its name and type
+        sql_pk = (
+            "SELECT a.attname, format_type(a.atttypid, a.atttypmod) AS data_type "
+            "FROM   pg_index i "
+            "JOIN   pg_attribute a ON a.attrelid = i.indrelid "
+            "AND a.attnum = ANY(i.indkey) "
+            "WHERE  i.indrelid = 'qgis_test.pk_lowercase'::regclass "
+            "AND    i.indisprimary;"
+        )
+        cur.execute(sql_pk)
+        self.assertEqual(cur.fetchall(), [('dep', 'character varying')])
+
 
 class TestPyQgsPostgresProviderCompoundKey(QgisTestCase, ProviderTestCase):