diff --git a/src/paperless_ai/indexing.py b/src/paperless_ai/indexing.py
index c8c9ebf46..4230edb8d 100644
--- a/src/paperless_ai/indexing.py
+++ b/src/paperless_ai/indexing.py
@@ -297,6 +297,23 @@ def _document_id_filters(doc_ids):
     )
 
 
+def _exclude_document_id_filter(document_id: int | str):
+    """Return a MetadataFilters NE filter excluding ``document_id``."""
+    from llama_index.core.vector_stores.types import FilterOperator
+    from llama_index.core.vector_stores.types import MetadataFilter
+    from llama_index.core.vector_stores.types import MetadataFilters
+
+    return MetadataFilters(
+        filters=[
+            MetadataFilter(
+                key="document_id",
+                operator=FilterOperator.NE,
+                value=str(document_id),
+            ),
+        ],
+    )
+
+
 def update_llm_index(
     *,
     iter_wrapper: IterWrapper[Document] = identity,
@@ -481,10 +498,18 @@ def query_similar_documents(
     config = AIConfig()
 
     from llama_index.core.retrievers import VectorIndexRetriever
+    from llama_index.core.vector_stores.types import FilterCondition
+    from llama_index.core.vector_stores.types import MetadataFilters
+
+    filter_parts = []
+    if allowed_document_ids is not None:
+        filter_parts.extend(_document_id_filters(allowed_document_ids).filters)
+    if document.pk is not None:
+        filter_parts.extend(_exclude_document_id_filter(document.pk).filters)
 
     filters = (
-        _document_id_filters(allowed_document_ids)
-        if allowed_document_ids is not None
+        MetadataFilters(filters=filter_parts, condition=FilterCondition.AND)
+        if filter_parts
         else None
     )
 
diff --git a/src/paperless_ai/tests/test_ai_indexing.py b/src/paperless_ai/tests/test_ai_indexing.py
index c15cc479b..c73959895 100644
--- a/src/paperless_ai/tests/test_ai_indexing.py
+++ b/src/paperless_ai/tests/test_ai_indexing.py
@@ -772,3 +772,33 @@ class TestQuerySimilarDocuments:
         results = indexing.query_similar_documents(a, document_ids=[b.id])
 
         assert all(doc.id == b.id for doc in results)
+
+    def test_query_similar_documents_excludes_self(
+        self,
+        temp_llm_index_dir: Path,
+        mock_embed_model: FakeEmbedding,
+    ) -> None:
+        a = DocumentFactory.create(content="alpha shared content here")
+        b = DocumentFactory.create(content="beta shared content here")
+        for doc in (a, b):
+            indexing.llm_index_add_or_update_document(doc)
+
+        results = indexing.query_similar_documents(a, top_k=5)
+
+        assert [doc.id for doc in results] == [b.id]
+
+    def test_query_similar_documents_excludes_self_with_multiple_chunks(
+        self,
+        temp_llm_index_dir: Path,
+        mock_embed_model: FakeEmbedding,
+    ) -> None:
+        # Document `a` is split into many chunks, so it could otherwise
+        # occupy several of the top-k slots with its own content.
+        a = DocumentFactory.create(content="word " * 4000)
+        b = DocumentFactory.create(content="beta shared content here")
+        for doc in (a, b):
+            indexing.llm_index_add_or_update_document(doc)
+
+        results = indexing.query_similar_documents(a, top_k=3)
+
+        assert [doc.id for doc in results] == [b.id]
diff --git a/src/paperless_ai/tests/test_vector_store.py b/src/paperless_ai/tests/test_vector_store.py
index 7fa4a5a6b..75cc0d17e 100644
--- a/src/paperless_ai/tests/test_vector_store.py
+++ b/src/paperless_ai/tests/test_vector_store.py
@@ -77,6 +77,18 @@ def _in_filter(document_ids: list[str]):
     )
 
 
+def _ne_filter(document_id: str):
+    return MetadataFilters(
+        filters=[
+            MetadataFilter(
+                key="document_id",
+                operator=FilterOperator.NE,
+                value=document_id,
+            ),
+        ],
+    )
+
+
 class TestCrud:
     def test_add_then_query_returns_node(self, store) -> None:
         node = make_node("n1", "1")
@@ -172,6 +184,19 @@ class TestCrud:
 
 
 class TestBuildWhere:
+    def test_ne_filter_translates_to_not_equal_clause(self) -> None:
+        where, params = _build_where(_ne_filter("1"))
+        assert where == "(document_id != ?)"
+        assert params == ["1"]
+
+    def test_query_with_ne_filter_excludes_matching_document(self, store) -> None:
+        store.add([make_node("a1", "1"), make_node("b1", "2")])
+        assert sorted(
+            _query(store, [0.0] * DIM, top_k=5, filters=_ne_filter("1")).ids,
+        ) == [
+            "b1",
+        ]
+
     def test_fails_closed_when_no_filter_is_translatable(self) -> None:
         # A nested MetadataFilters is not a MetadataFilter, so it is skipped.
         # With no translatable clauses, the function must fail closed rather
diff --git a/src/paperless_ai/vector_store.py b/src/paperless_ai/vector_store.py
index d44583d22..f6f333576 100644
--- a/src/paperless_ai/vector_store.py
+++ b/src/paperless_ai/vector_store.py
@@ -94,7 +94,7 @@ def _unpack(blob: bytes) -> list[float]:
 
 
 def _build_where(filters: MetadataFilters | None) -> tuple[str, list[str]]:
-    """Translate the EQ / IN filters we use into a parameterized SQL clause
+    """Translate the EQ / IN / NE filters we use into a parameterized SQL clause
     on vec0 metadata columns. Returns ("", []) when there is nothing to filter.
     """
     if filters is None or not filters.filters:
@@ -119,7 +119,10 @@ def _build_where(filters: MetadataFilters | None) -> tuple[str, list[str]]:
         elif f.operator == FilterOperator.EQ:
             clauses.append(f"{f.key} = ?")
             params.append(str(f.value))
-        else:  # pragma: no cover - we only ever build EQ/IN filters
+        elif f.operator == FilterOperator.NE:
+            clauses.append(f"{f.key} != ?")
+            params.append(str(f.value))
+        else:  # pragma: no cover - we only ever build EQ/IN/NE filters
             raise NotImplementedError(f"Unsupported filter operator: {f.operator}")
     if not clauses:
         # Filters were requested but none could be translated. Fail closed