diff --git a/chain/store/store.go b/chain/store/store.go
index dba5995de..e3d6506e4 100644
--- a/chain/store/store.go
+++ b/chain/store/store.go
@@ -47,6 +47,7 @@ import (
 var log = logging.Logger("chainstore")
 
 var chainHeadKey = dstore.NewKey("head")
+var blockValidationCacheKeyPrefix = dstore.NewKey("blockValidation")
 
 type ChainStore struct {
 	bs bstore.Blockstore
@@ -215,6 +216,22 @@ func (cs *ChainStore) SubscribeHeadChanges(f func(rev, app []*types.TipSet) erro
 	cs.headChangeNotifs = append(cs.headChangeNotifs, f)
 }
 
+func (cs *ChainStore) IsBlockValidated(ctx context.Context, blkid cid.Cid) (bool, error) {
+	key := blockValidationCacheKeyPrefix.Instance(blkid.String())
+
+	return cs.ds.Has(key)
+}
+
+func (cs *ChainStore) MarkBlockAsValidated(ctx context.Context, blkid cid.Cid) error {
+	key := blockValidationCacheKeyPrefix.Instance(blkid.String())
+
+	if err := cs.ds.Put(key, []byte{0}); err != nil {
+		return xerrors.Errorf("cache block validation: %w", err)
+	}
+
+	return nil
+}
+
 func (cs *ChainStore) SetGenesis(b *types.BlockHeader) error {
 	ts, err := types.NewTipSet([]*types.BlockHeader{b})
 	if err != nil {
diff --git a/chain/sync.go b/chain/sync.go
index 05c0bc7cf..20e57c25d 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -529,7 +529,24 @@ func blockSanityChecks(h *types.BlockHeader) error {
 }
 
 // Should match up with 'Semantical Validation' in validation.md in the spec
-func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) error {
+func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) (err error) {
+	defer func() {
+		// b.Cid() could panic for empty blocks that are used in tests.
+		if rerr := recover(); rerr != nil {
+			err = xerrors.Errorf("validate block panic: %w", rerr)
+			return
+		}
+	}()
+
+	isValidated, err := syncer.store.IsBlockValidated(ctx, b.Cid())
+	if err != nil {
+		return xerrors.Errorf("check block validation cache %s: %w", b.Cid(), err)
+	}
+
+	if isValidated {
+		return nil
+	}
+
 	validationStart := time.Now()
 	defer func() {
 		dur := time.Since(validationStart)
@@ -759,7 +776,11 @@ func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) err
 		}
 	}
 
-	return merr
+	if err := syncer.store.MarkBlockAsValidated(ctx, b.Cid()); err != nil {
+		return xerrors.Errorf("caching block validation %s: %w", b.Cid(), err)
+	}
+
+	return nil
 }
 
 func (syncer *Syncer) VerifyWinningPoStProof(ctx context.Context, h *types.BlockHeader, prevBeacon types.BeaconEntry, lbst cid.Cid, waddr address.Address) error {