diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index 23e99841e..87b440edc 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -258,16 +258,35 @@ func (s *Service) ancestor(ctx context.Context, root []byte, slot uint64) ([]byt
 	ctx, span := trace.StartSpan(ctx, "forkChoice.ancestor")
 	defer span.End()
 
-	// Stop recursive ancestry lookup if context is cancelled.
-	if ctx.Err() != nil {
-		return nil, ctx.Err()
-	}
-
 	r := bytesutil.ToBytes32(root)
 	// Get ancestor root from fork choice store instead of recursively looking up blocks in DB.
 	// This is most optimal outcome.
-	if s.forkChoiceStore.HasParent(r) {
-		return s.forkChoiceStore.AncestorRoot(ctx, r, slot)
+	ar, err := s.ancestorByForkChoiceStore(ctx, r, slot)
+	if err != nil {
+		// Try getting ancestor root from DB when failed to retrieve from fork choice store.
+		// This is the second line of defense for retrieving ancestor root.
+		ar, err = s.ancestorByDB(ctx, r, slot)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return ar, nil
+}
+
+// This retrieves an ancestor root using fork choice store. The look up is looping through the a flat array structure.
+func (s *Service) ancestorByForkChoiceStore(ctx context.Context, r [32]byte, slot uint64) ([]byte, error) {
+	if !s.forkChoiceStore.HasParent(r) {
+		return nil, errors.New("could not find root in fork choice store")
+	}
+	return s.forkChoiceStore.AncestorRoot(ctx, r, slot)
+}
+
+// This retrieves an ancestor root using DB. The look up is recursively looking up DB. Slower than `ancestorByForkChoiceStore`.
+func (s *Service) ancestorByDB(ctx context.Context, r [32]byte, slot uint64) ([]byte, error) {
+	// Stop recursive ancestry lookup if context is cancelled.
+	if ctx.Err() != nil {
+		return nil, ctx.Err()
 	}
 
 	signed, err := s.beaconDB.Block(ctx, r)
@@ -284,10 +303,10 @@ func (s *Service) ancestor(ctx context.Context, root []byte, slot uint64) ([]byt
 	}
 	b := signed.Block
 	if b.Slot == slot || b.Slot < slot {
-		return root, nil
+		return r[:], nil
 	}
 
-	return s.ancestor(ctx, b.ParentRoot, slot)
+	return s.ancestorByDB(ctx, bytesutil.ToBytes32(b.ParentRoot), slot)
 }
 
 // This updates justified check point in store, if the new justified is later than stored justified or
diff --git a/beacon-chain/blockchain/process_block_test.go b/beacon-chain/blockchain/process_block_test.go
index 44ccd21fa..a8493e22c 100644
--- a/beacon-chain/blockchain/process_block_test.go
+++ b/beacon-chain/blockchain/process_block_test.go
@@ -516,6 +516,15 @@ func TestCurrentSlot_HandlesOverflow(t *testing.T) {
 	slot := svc.CurrentSlot()
 	require.Equal(t, uint64(0), slot, "Unexpected slot")
 }
+func TestAncestorByDB_CtxErr(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	service, err := NewService(ctx, &Config{})
+	require.NoError(t, err)
+
+	cancel()
+	_, err = service.ancestorByDB(ctx, [32]byte{}, 0)
+	require.ErrorContains(t, "context canceled", err)
+}
 
 func TestAncestor_HandleSkipSlot(t *testing.T) {
 	ctx := context.Background()
@@ -562,6 +571,82 @@ func TestAncestor_HandleSkipSlot(t *testing.T) {
 	}
 }
 
+func TestAncestor_CanUseForkchoice(t *testing.T) {
+	ctx := context.Background()
+	cfg := &Config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
+	service, err := NewService(ctx, cfg)
+	require.NoError(t, err)
+
+	b1 := testutil.NewBeaconBlock()
+	b1.Block.Slot = 1
+	b1.Block.ParentRoot = bytesutil.PadTo([]byte{'a'}, 32)
+	r1, err := b1.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b100 := testutil.NewBeaconBlock()
+	b100.Block.Slot = 100
+	b100.Block.ParentRoot = r1[:]
+	r100, err := b100.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b200 := testutil.NewBeaconBlock()
+	b200.Block.Slot = 200
+	b200.Block.ParentRoot = r100[:]
+	r200, err := b200.Block.HashTreeRoot()
+	require.NoError(t, err)
+	for _, b := range []*ethpb.SignedBeaconBlock{b1, b100, b200} {
+		beaconBlock := testutil.NewBeaconBlock()
+		beaconBlock.Block.Slot = b.Block.Slot
+		beaconBlock.Block.ParentRoot = bytesutil.PadTo(b.Block.ParentRoot, 32)
+		r, err := b.Block.HashTreeRoot()
+		require.NoError(t, err)
+		require.NoError(t, service.forkChoiceStore.ProcessBlock(context.Background(), b.Block.Slot, r, bytesutil.ToBytes32(b.Block.ParentRoot), [32]byte{}, 0, 0)) // Saves blocks to fork choice store.
+	}
+
+	r, err := service.ancestor(context.Background(), r200[:], 150)
+	require.NoError(t, err)
+	if bytesutil.ToBytes32(r) != r100 {
+		t.Error("Did not get correct root")
+	}
+}
+
+func TestAncestor_CanUseDB(t *testing.T) {
+	ctx := context.Background()
+	db, _ := testDB.SetupDB(t)
+
+	cfg := &Config{BeaconDB: db, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
+	service, err := NewService(ctx, cfg)
+	require.NoError(t, err)
+
+	b1 := testutil.NewBeaconBlock()
+	b1.Block.Slot = 1
+	b1.Block.ParentRoot = bytesutil.PadTo([]byte{'a'}, 32)
+	r1, err := b1.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b100 := testutil.NewBeaconBlock()
+	b100.Block.Slot = 100
+	b100.Block.ParentRoot = r1[:]
+	r100, err := b100.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b200 := testutil.NewBeaconBlock()
+	b200.Block.Slot = 200
+	b200.Block.ParentRoot = r100[:]
+	r200, err := b200.Block.HashTreeRoot()
+	require.NoError(t, err)
+	for _, b := range []*ethpb.SignedBeaconBlock{b1, b100, b200} {
+		beaconBlock := testutil.NewBeaconBlock()
+		beaconBlock.Block.Slot = b.Block.Slot
+		beaconBlock.Block.ParentRoot = bytesutil.PadTo(b.Block.ParentRoot, 32)
+		require.NoError(t, db.SaveBlock(context.Background(), beaconBlock)) // Saves blocks to DB.
+	}
+
+	require.NoError(t, service.forkChoiceStore.ProcessBlock(context.Background(), 200, r200, r200, [32]byte{}, 0, 0))
+
+	r, err := service.ancestor(context.Background(), r200[:], 150)
+	require.NoError(t, err)
+	if bytesutil.ToBytes32(r) != r100 {
+		t.Error("Did not get correct root")
+	}
+}
+
 func TestEnsureRootNotZeroHashes(t *testing.T) {
 	ctx := context.Background()
 	cfg := &Config{}