diff --git a/beacon-chain/sync/pending_blocks_queue.go b/beacon-chain/sync/pending_blocks_queue.go
index 568370a99..c3439e5f4 100644
--- a/beacon-chain/sync/pending_blocks_queue.go
+++ b/beacon-chain/sync/pending_blocks_queue.go
@@ -55,6 +55,9 @@ func (s *Service) processPendingBlocks(ctx context.Context) error {
 	ctx, span := trace.StartSpan(ctx, "processPendingBlocks")
 	defer span.End()
 
+	// Remove old blocks from our expiration cache.
+	s.deleteExpiredBlocksFromCache()
+
 	// Validate pending slots before processing.
 	if err := s.validatePendingSlots(); err != nil {
 		return errors.Wrap(err, "could not validate pending slots")
@@ -432,6 +435,15 @@ func (s *Service) deleteBlockFromPendingQueue(slot primitives.Slot, b interfaces
 	return nil
 }
 
+// This method manually clears our cache so that all expired
+// entries are correctly removed.
+func (s *Service) deleteExpiredBlocksFromCache() {
+	s.pendingQueueLock.Lock()
+	defer s.pendingQueueLock.Unlock()
+
+	s.slotToPendingBlocks.DeleteExpired()
+}
+
 // Insert block to the list in the pending queue using the slot as key.
 // Note: this helper is not thread safe.
 func (s *Service) insertBlockToPendingQueue(_ primitives.Slot, b interfaces.ReadOnlySignedBeaconBlock, r [32]byte) error {
diff --git a/beacon-chain/sync/pending_blocks_queue_test.go b/beacon-chain/sync/pending_blocks_queue_test.go
index a21aacb0f..2bde21a27 100644
--- a/beacon-chain/sync/pending_blocks_queue_test.go
+++ b/beacon-chain/sync/pending_blocks_queue_test.go
@@ -884,3 +884,61 @@ func TestAlreadySyncingBlock(t *testing.T) {
 	require.NoError(t, r.processPendingBlocks(ctx))
 	require.LogsContain(t, hook, "Skipping pending block already being processed")
 }
+
+func TestExpirationCache_PruneOldBlocksCorrectly(t *testing.T) {
+	ctx := context.Background()
+	db := dbtest.SetupDB(t)
+
+	mockChain := &mock.ChainService{
+		FinalizedCheckPoint: &ethpb.Checkpoint{
+			Epoch: 0,
+		},
+	}
+
+	p1 := p2ptest.NewTestP2P(t)
+	// Reset expiration time
+	currExpTime := pendingBlockExpTime
+	defer func() {
+		pendingBlockExpTime = currExpTime
+	}()
+	pendingBlockExpTime = 500 * time.Millisecond
+
+	r := NewService(ctx,
+		WithStateGen(stategen.New(db, doublylinkedtree.New())),
+		WithDatabase(db),
+		WithChainService(mockChain),
+		WithP2P(p1),
+	)
+	b1 := util.NewBeaconBlock()
+	b1.Block.Slot = 1
+	b1.Block.ProposerIndex = 10
+	b1Root, err := b1.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err := blocks.NewSignedBeaconBlock(b1)
+	require.NoError(t, err)
+	require.NoError(t, r.insertBlockToPendingQueue(1, wsb, b1Root))
+
+	// Add new block with the same slot.
+	b2 := util.NewBeaconBlock()
+	b2.Block.Slot = 1
+	b2.Block.ProposerIndex = 11
+	b2Root, err := b2.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err = blocks.NewSignedBeaconBlock(b2)
+	require.NoError(t, err)
+	require.NoError(t, r.insertBlockToPendingQueue(1, wsb, b2Root))
+
+	require.Equal(t, true, r.seenPendingBlocks[b1Root])
+	require.Equal(t, true, r.seenPendingBlocks[b2Root])
+	require.Equal(t, 2, len(r.pendingBlocksInCache(1)))
+
+	// Wait for expiration cache to cleanup and remove old block.
+	time.Sleep(2 * pendingBlockExpTime)
+
+	// Run pending queue with expired blocks.
+	require.NoError(t, r.processPendingBlocks(ctx))
+
+	assert.Equal(t, false, r.seenPendingBlocks[b1Root])
+	assert.Equal(t, false, r.seenPendingBlocks[b2Root])
+	assert.Equal(t, 0, len(r.pendingBlocksInCache(1)))
+}
diff --git a/beacon-chain/sync/service.go b/beacon-chain/sync/service.go
index 8adcca900..fe3378fe7 100644
--- a/beacon-chain/sync/service.go
+++ b/beacon-chain/sync/service.go
@@ -34,11 +34,13 @@ import (
 	"github.com/prysmaticlabs/prysm/v4/beacon-chain/state/stategen"
 	lruwrpr "github.com/prysmaticlabs/prysm/v4/cache/lru"
 	"github.com/prysmaticlabs/prysm/v4/config/params"
+	"github.com/prysmaticlabs/prysm/v4/consensus-types/interfaces"
 	leakybucket "github.com/prysmaticlabs/prysm/v4/container/leaky-bucket"
 	ethpb "github.com/prysmaticlabs/prysm/v4/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/v4/runtime"
 	prysmTime "github.com/prysmaticlabs/prysm/v4/time"
 	"github.com/prysmaticlabs/prysm/v4/time/slots"
+	"github.com/trailofbits/go-mutexasserts"
 )
 
 var _ runtime.Service = (*Service)(nil)
@@ -152,7 +154,7 @@ type Service struct {
 
 // NewService initializes new regular sync service.
 func NewService(ctx context.Context, opts ...Option) *Service {
-	c := gcache.New(pendingBlockExpTime /* exp time */, 2*pendingBlockExpTime /* prune time */)
+	c := gcache.New(pendingBlockExpTime /* exp time */, 0 /* disable janitor */)
 	ctx, cancel := context.WithCancel(ctx)
 	r := &Service{
 		ctx:                  ctx,
@@ -170,6 +172,28 @@ func NewService(ctx context.Context, opts ...Option) *Service {
 			return nil
 		}
 	}
+	// Correctly remove it from our seen pending block map.
+	// The eviction method always assumes that the mutex is held.
+	r.slotToPendingBlocks.OnEvicted(func(s string, i interface{}) {
+		if !mutexasserts.RWMutexLocked(&r.pendingQueueLock) {
+			log.Errorf("Mutex is not locked during cache eviction of values")
+			// Continue on to allow elements to be properly removed.
+		}
+		blks, ok := i.([]interfaces.ReadOnlySignedBeaconBlock)
+		if !ok {
+			log.Errorf("Invalid type retrieved from the cache: %T", i)
+			return
+		}
+
+		for _, b := range blks {
+			root, err := b.Block().HashTreeRoot()
+			if err != nil {
+				log.WithError(err).Error("Could not calculate htr of block")
+				continue
+			}
+			delete(r.seenPendingBlocks, root)
+		}
+	})
 	r.subHandler = newSubTopicHandler()
 	r.rateLimiter = newRateLimiter(r.cfg.p2p)
 	r.initCaches()