diff --git a/src/sqlfluff/dialects/dialect_trino.py b/src/sqlfluff/dialects/dialect_trino.py
index 72c4a3c3b57..4a8fa3ff1b9 100644
--- a/src/sqlfluff/dialects/dialect_trino.py
+++ b/src/sqlfluff/dialects/dialect_trino.py
@@ -396,6 +396,11 @@ class WithinGroupClauseSegment(BaseSegment):
     """An WITHIN GROUP clause for window functions.
 
     https://trino.io/docs/current/functions/aggregate.html#array_agg
+
+    Trino supports an optional FILTER during aggregation that comes
+    immediately after the WITHIN GROUP clause.
+
+    https://trino.io/docs/current/functions/aggregate.html#filtering-during-aggregation
     """
 
     type = "withingroup_clause"
@@ -403,6 +408,7 @@ class WithinGroupClauseSegment(BaseSegment):
         "WITHIN",
         "GROUP",
         Bracketed(Ref("OrderByClauseSegment", optional=False)),
+        Ref("FilterClauseGrammar", optional=True),
     )
 
 
diff --git a/test/fixtures/dialects/trino/filter_aggregate.sql b/test/fixtures/dialects/trino/filter_aggregate.sql
new file mode 100644
index 00000000000..1a5f255788d
--- /dev/null
+++ b/test/fixtures/dialects/trino/filter_aggregate.sql
@@ -0,0 +1,11 @@
+SELECT id,
+       COUNT(*) FILTER (WHERE o IS NOT NULL) AS count
+FROM (VALUES
+    (100, 2, 'a'),
+    (100, 1, 'b'),
+    (200, NULL, 'c'),
+    (200, 2, 'a'),
+    (300, NULL, 'b'),
+    (300, NULL, 'c')
+) t(id, o, value)
+GROUP BY id;
diff --git a/test/fixtures/dialects/trino/filter_aggregate.yml b/test/fixtures/dialects/trino/filter_aggregate.yml
new file mode 100644
index 00000000000..52b9f77d4e6
--- /dev/null
+++ b/test/fixtures/dialects/trino/filter_aggregate.yml
@@ -0,0 +1,123 @@
+# YML test files are auto-generated from SQL files and should not be edited by
+# hand. To help enforce this, the "hash" field in the file must match a hash
+# computed by SQLFluff when running the tests. Please run
+# `python test/generate_parse_fixture_yml.py`  to generate them after adding or
+# altering SQL files.
+_hash: 464b6edb476473531ba7dc5e1453ce36ca8b444d588ad3d41543bc754fb6faee
+file:
+  statement:
+    select_statement:
+      select_clause:
+      - keyword: SELECT
+      - select_clause_element:
+          column_reference:
+            naked_identifier: id
+      - comma: ','
+      - select_clause_element:
+          function:
+          - function_name:
+              function_name_identifier: COUNT
+          - bracketed:
+              start_bracket: (
+              star: '*'
+              end_bracket: )
+          - keyword: FILTER
+          - bracketed:
+              start_bracket: (
+              keyword: WHERE
+              expression:
+              - column_reference:
+                  naked_identifier: o
+              - keyword: IS
+              - keyword: NOT
+              - null_literal: 'NULL'
+              end_bracket: )
+          alias_expression:
+            keyword: AS
+            naked_identifier: count
+      from_clause:
+        keyword: FROM
+        from_expression:
+          from_expression_element:
+            bracketed:
+              start_bracket: (
+              table_expression:
+                values_clause:
+                - keyword: VALUES
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '100'
+                    - comma: ','
+                    - numeric_literal: '2'
+                    - comma: ','
+                    - quoted_literal: "'a'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '100'
+                    - comma: ','
+                    - numeric_literal: '1'
+                    - comma: ','
+                    - quoted_literal: "'b'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '200'
+                    - comma: ','
+                    - null_literal: 'NULL'
+                    - comma: ','
+                    - quoted_literal: "'c'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '200'
+                    - comma: ','
+                    - numeric_literal: '2'
+                    - comma: ','
+                    - quoted_literal: "'a'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '300'
+                    - comma: ','
+                    - null_literal: 'NULL'
+                    - comma: ','
+                    - quoted_literal: "'b'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '300'
+                    - comma: ','
+                    - null_literal: 'NULL'
+                    - comma: ','
+                    - quoted_literal: "'c'"
+                    - end_bracket: )
+              end_bracket: )
+            alias_expression:
+              naked_identifier: t
+              bracketed:
+                start_bracket: (
+                identifier_list:
+                - naked_identifier: id
+                - comma: ','
+                - naked_identifier: o
+                - comma: ','
+                - naked_identifier: value
+                end_bracket: )
+      groupby_clause:
+      - keyword: GROUP
+      - keyword: BY
+      - column_reference:
+          naked_identifier: id
+  statement_terminator: ;
diff --git a/test/fixtures/dialects/trino/within_group.sql b/test/fixtures/dialects/trino/within_group.sql
index fae5287b0a4..689e791dedb 100644
--- a/test/fixtures/dialects/trino/within_group.sql
+++ b/test/fixtures/dialects/trino/within_group.sql
@@ -17,3 +17,16 @@ FROM (VALUES
 ) t(id, o, value)
 GROUP BY id
 ORDER BY id;
+
+-- Handle a WITHIN GROUP followed by a FILTER
+SELECT id, LISTAGG(value, ',') WITHIN GROUP (ORDER BY o) FILTER (WHERE o IS NOT NULL) AS csv_value
+FROM (VALUES
+    (100, 2, 'a'),
+    (100, 1, 'b'),
+    (200, NULL, 'c'),
+    (200, 2, 'a'),
+    (300, NULL, 'b'),
+    (300, 1, 'c')
+) t(id, o, value)
+GROUP BY id
+ORDER BY id;
diff --git a/test/fixtures/dialects/trino/within_group.yml b/test/fixtures/dialects/trino/within_group.yml
index d72167cc657..12ab1964f87 100644
--- a/test/fixtures/dialects/trino/within_group.yml
+++ b/test/fixtures/dialects/trino/within_group.yml
@@ -3,7 +3,7 @@
 # computed by SQLFluff when running the tests. Please run
 # `python test/generate_parse_fixture_yml.py`  to generate them after adding or
 # altering SQL files.
-_hash: cd402a357356eace79b2dc1ae0f7d1915e1b42f0bb860dd9c483b51ea4ba5822
+_hash: 016faab7c8653d99929df73b008bfdf51c5bc3609a6ce6e3b79843e36092f735
 file:
 - statement:
     select_statement:
@@ -277,3 +277,140 @@ file:
       - column_reference:
           naked_identifier: id
 - statement_terminator: ;
+- statement:
+    select_statement:
+      select_clause:
+      - keyword: SELECT
+      - select_clause_element:
+          column_reference:
+            naked_identifier: id
+      - comma: ','
+      - select_clause_element:
+          function:
+            function_name:
+              function_name_identifier: LISTAGG
+            bracketed:
+            - start_bracket: (
+            - expression:
+                column_reference:
+                  naked_identifier: value
+            - comma: ','
+            - expression:
+                quoted_literal: "','"
+            - end_bracket: )
+            withingroup_clause:
+            - keyword: WITHIN
+            - keyword: GROUP
+            - bracketed:
+                start_bracket: (
+                orderby_clause:
+                - keyword: ORDER
+                - keyword: BY
+                - column_reference:
+                    naked_identifier: o
+                end_bracket: )
+            - keyword: FILTER
+            - bracketed:
+                start_bracket: (
+                keyword: WHERE
+                expression:
+                - column_reference:
+                    naked_identifier: o
+                - keyword: IS
+                - keyword: NOT
+                - null_literal: 'NULL'
+                end_bracket: )
+          alias_expression:
+            keyword: AS
+            naked_identifier: csv_value
+      from_clause:
+        keyword: FROM
+        from_expression:
+          from_expression_element:
+            bracketed:
+              start_bracket: (
+              table_expression:
+                values_clause:
+                - keyword: VALUES
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '100'
+                    - comma: ','
+                    - numeric_literal: '2'
+                    - comma: ','
+                    - quoted_literal: "'a'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '100'
+                    - comma: ','
+                    - numeric_literal: '1'
+                    - comma: ','
+                    - quoted_literal: "'b'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '200'
+                    - comma: ','
+                    - null_literal: 'NULL'
+                    - comma: ','
+                    - quoted_literal: "'c'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '200'
+                    - comma: ','
+                    - numeric_literal: '2'
+                    - comma: ','
+                    - quoted_literal: "'a'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '300'
+                    - comma: ','
+                    - null_literal: 'NULL'
+                    - comma: ','
+                    - quoted_literal: "'b'"
+                    - end_bracket: )
+                - comma: ','
+                - expression:
+                    bracketed:
+                    - start_bracket: (
+                    - numeric_literal: '300'
+                    - comma: ','
+                    - numeric_literal: '1'
+                    - comma: ','
+                    - quoted_literal: "'c'"
+                    - end_bracket: )
+              end_bracket: )
+            alias_expression:
+              naked_identifier: t
+              bracketed:
+                start_bracket: (
+                identifier_list:
+                - naked_identifier: id
+                - comma: ','
+                - naked_identifier: o
+                - comma: ','
+                - naked_identifier: value
+                end_bracket: )
+      groupby_clause:
+      - keyword: GROUP
+      - keyword: BY
+      - column_reference:
+          naked_identifier: id
+      orderby_clause:
+      - keyword: ORDER
+      - keyword: BY
+      - column_reference:
+          naked_identifier: id
+- statement_terminator: ;