diff --git a/src/backend/access/transam/README.parallel b/src/backend/access/transam/README.parallel
index f09a5806345..85e5840feba 100644
--- a/src/backend/access/transam/README.parallel
+++ b/src/backend/access/transam/README.parallel
@@ -125,6 +125,10 @@ worker.  This includes:
   - State related to pending REINDEX operations, which prevents access to
     an index that is currently being rebuilt.
 
+  - Active relmapper.c mapping state.  This is needed to allow consistent
+    answers when fetching the current relfilenode for relation oids of
+    mapped relations.
+
 To prevent unprincipled deadlocks when running in parallel mode, this code
 also arranges for the leader and all workers to participate in group
 locking.  See src/backend/storage/lmgr/README for more details.
diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index 30ddf94c952..c1681184670 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -37,6 +37,7 @@
 #include "utils/guc.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
+#include "utils/relmapper.h"
 #include "utils/snapmgr.h"
 #include "utils/typcache.h"
 
@@ -69,6 +70,7 @@
 #define PARALLEL_KEY_ENTRYPOINT				UINT64CONST(0xFFFFFFFFFFFF0009)
 #define PARALLEL_KEY_SESSION_DSM			UINT64CONST(0xFFFFFFFFFFFF000A)
 #define PARALLEL_KEY_REINDEX_STATE			UINT64CONST(0xFFFFFFFFFFFF000B)
+#define PARALLEL_KEY_RELMAPPER_STATE		UINT64CONST(0xFFFFFFFFFFFF000C)
 
 /* Fixed-size parallel state. */
 typedef struct FixedParallelState
@@ -205,6 +207,7 @@ InitializeParallelDSM(ParallelContext *pcxt)
 	Size		asnaplen = 0;
 	Size		tstatelen = 0;
 	Size		reindexlen = 0;
+	Size		relmapperlen = 0;
 	Size		segsize = 0;
 	int			i;
 	FixedParallelState *fps;
@@ -256,8 +259,10 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		shm_toc_estimate_chunk(&pcxt->estimator, sizeof(dsm_handle));
 		reindexlen = EstimateReindexStateSpace();
 		shm_toc_estimate_chunk(&pcxt->estimator, reindexlen);
+		relmapperlen = EstimateRelationMapSpace();
+		shm_toc_estimate_chunk(&pcxt->estimator, relmapperlen);
 		/* If you add more chunks here, you probably need to add keys. */
-		shm_toc_estimate_keys(&pcxt->estimator, 8);
+		shm_toc_estimate_keys(&pcxt->estimator, 9);
 
 		/* Estimate space need for error queues. */
 		StaticAssertStmt(BUFFERALIGN(PARALLEL_ERROR_QUEUE_SIZE) ==
@@ -327,6 +332,7 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		char	   *asnapspace;
 		char	   *tstatespace;
 		char	   *reindexspace;
+		char	   *relmapperspace;
 		char	   *error_queue_space;
 		char	   *session_dsm_handle_space;
 		char	   *entrypointstate;
@@ -373,6 +379,12 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		SerializeReindexState(reindexlen, reindexspace);
 		shm_toc_insert(pcxt->toc, PARALLEL_KEY_REINDEX_STATE, reindexspace);
 
+		/* Serialize relmapper state. */
+		relmapperspace = shm_toc_allocate(pcxt->toc, relmapperlen);
+		SerializeRelationMap(relmapperlen, relmapperspace);
+		shm_toc_insert(pcxt->toc, PARALLEL_KEY_RELMAPPER_STATE,
+					   relmapperspace);
+
 		/* Allocate space for worker information. */
 		pcxt->worker = palloc0(sizeof(ParallelWorkerInfo) * pcxt->nworkers);
 
@@ -1205,6 +1217,7 @@ ParallelWorkerMain(Datum main_arg)
 	char	   *asnapspace;
 	char	   *tstatespace;
 	char	   *reindexspace;
+	char	   *relmapperspace;
 	StringInfoData msgbuf;
 	char	   *session_dsm_handle_space;
 
@@ -1380,6 +1393,10 @@ ParallelWorkerMain(Datum main_arg)
 	reindexspace = shm_toc_lookup(toc, PARALLEL_KEY_REINDEX_STATE, false);
 	RestoreReindexState(reindexspace);
 
+	/* Restore relmapper state. */
+	relmapperspace = shm_toc_lookup(toc, PARALLEL_KEY_RELMAPPER_STATE, false);
+	RestoreRelationMap(relmapperspace);
+
 	/*
 	 * We've initialized all of our state now; nothing should change
 	 * hereafter.
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 9aa63c8792b..cd8270d5fb0 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -2018,7 +2018,7 @@ CommitTransaction(void)
 	HOLD_INTERRUPTS();
 
 	/* Commit updates to the relation map --- do this as late as possible */
-	AtEOXact_RelationMap(true);
+	AtEOXact_RelationMap(true, is_parallel_worker);
 
 	/*
 	 * set the current transaction state information appropriately during
@@ -2539,7 +2539,7 @@ AbortTransaction(void)
 	AtAbort_Portals();
 	AtEOXact_LargeObject(false);
 	AtAbort_Notify();
-	AtEOXact_RelationMap(false);
+	AtEOXact_RelationMap(false, is_parallel_worker);
 	AtAbort_Twophase();
 
 	/*
diff --git a/src/backend/utils/cache/relmapper.c b/src/backend/utils/cache/relmapper.c
index c7f0e6f6d4a..905867dc767 100644
--- a/src/backend/utils/cache/relmapper.c
+++ b/src/backend/utils/cache/relmapper.c
@@ -91,6 +91,16 @@ typedef struct RelMapFile
 	int32		pad;			/* to make the struct size be 512 exactly */
 } RelMapFile;
 
+/*
+ * State for serializing local and shared relmappings for parallel workers
+ * (active states only).  See notes on active_* and pending_* updates state.
+ */
+typedef struct SerializedActiveRelMaps
+{
+	RelMapFile	active_shared_updates;
+	RelMapFile	active_local_updates;
+} SerializedActiveRelMaps;
+
 /*
  * The currently known contents of the shared map file and our database's
  * local map file are stored here.  These can be reloaded from disk
@@ -111,6 +121,9 @@ static RelMapFile local_map;
  * they will become active at the next CommandCounterIncrement.  This setup
  * lets map updates act similarly to updates of pg_class rows, ie, they
  * become visible only at the next CommandCounterIncrement boundary.
+ *
+ * Active shared and active local updates are serialized by the parallel
+ * infrastructure, and deserialized within parallel workers.
  */
 static RelMapFile active_shared_updates;
 static RelMapFile active_local_updates;
@@ -263,13 +276,16 @@ RelationMapUpdateMap(Oid relationId, Oid fileNode, bool shared,
 	else
 	{
 		/*
-		 * We don't currently support map changes within subtransactions. This
-		 * could be done with more bookkeeping infrastructure, but it doesn't
-		 * presently seem worth it.
+		 * We don't currently support map changes within subtransactions, or
+		 * when in parallel mode.  This could be done with more bookkeeping
+		 * infrastructure, but it doesn't presently seem worth it.
 		 */
 		if (GetCurrentTransactionNestLevel() > 1)
 			elog(ERROR, "cannot change relation mapping within subtransaction");
 
+		if (IsInParallelMode())
+			elog(ERROR, "cannot change relation mapping in parallel mode");
+
 		if (immediate)
 		{
 			/* Make it active, but only locally */
@@ -452,11 +468,14 @@ AtCCI_RelationMap(void)
  *
  * During abort, we just have to throw away any pending map changes.
  * Normal post-abort cleanup will take care of fixing relcache entries.
+ * Parallel worker commit/abort is handled by resetting active mappings
+ * that may have been received from the leader process.  (There should be
+ * no pending updates in parallel workers.)
  */
 void
-AtEOXact_RelationMap(bool isCommit)
+AtEOXact_RelationMap(bool isCommit, bool isParallelWorker)
 {
-	if (isCommit)
+	if (isCommit && !isParallelWorker)
 	{
 		/*
 		 * We should not get here with any "pending" updates.  (We could
@@ -482,7 +501,10 @@ AtEOXact_RelationMap(bool isCommit)
 	}
 	else
 	{
-		/* Abort --- drop all local and pending updates */
+		/* Abort or parallel worker --- drop all local and pending updates */
+		Assert(!isParallelWorker || pending_shared_updates.num_mappings == 0);
+		Assert(!isParallelWorker || pending_local_updates.num_mappings == 0);
+
 		active_shared_updates.num_mappings = 0;
 		active_local_updates.num_mappings = 0;
 		pending_shared_updates.num_mappings = 0;
@@ -614,6 +636,56 @@ RelationMapInitializePhase3(void)
 	load_relmap_file(false);
 }
 
+/*
+ * EstimateRelationMapSpace
+ *
+ * Estimate space needed to pass active shared and local relmaps to parallel
+ * workers.
+ */
+Size
+EstimateRelationMapSpace(void)
+{
+	return sizeof(SerializedActiveRelMaps);
+}
+
+/*
+ * SerializeRelationMap
+ *
+ * Serialize active shared and local relmap state for parallel workers.
+ */
+void
+SerializeRelationMap(Size maxSize, char *startAddress)
+{
+	SerializedActiveRelMaps	   *relmaps;
+
+	Assert(maxSize >= EstimateRelationMapSpace());
+
+	relmaps = (SerializedActiveRelMaps *) startAddress;
+	relmaps->active_shared_updates = active_shared_updates;
+	relmaps->active_local_updates = active_local_updates;
+}
+
+/*
+ * RestoreRelationMap
+ *
+ * Restore active shared and local relmap state within a parallel worker.
+ */
+void
+RestoreRelationMap(char *startAddress)
+{
+	SerializedActiveRelMaps	   *relmaps;
+
+	if (active_shared_updates.num_mappings != 0 ||
+		active_local_updates.num_mappings != 0 ||
+		pending_shared_updates.num_mappings != 0 ||
+		pending_local_updates.num_mappings != 0)
+		elog(ERROR, "parallel worker has existing mappings");
+
+	relmaps = (SerializedActiveRelMaps *) startAddress;
+	active_shared_updates = relmaps->active_shared_updates;
+	active_local_updates = relmaps->active_local_updates;
+}
+
 /*
  * load_relmap_file -- load data from the shared or local map file
  *
diff --git a/src/include/utils/relmapper.h b/src/include/utils/relmapper.h
index f69b1006bf2..fb51943498d 100644
--- a/src/include/utils/relmapper.h
+++ b/src/include/utils/relmapper.h
@@ -48,7 +48,7 @@ extern void RelationMapInvalidate(bool shared);
 extern void RelationMapInvalidateAll(void);
 
 extern void AtCCI_RelationMap(void);
-extern void AtEOXact_RelationMap(bool isCommit);
+extern void AtEOXact_RelationMap(bool isCommit, bool isParallelWorker);
 extern void AtPrepare_RelationMap(void);
 
 extern void CheckPointRelationMap(void);
@@ -59,6 +59,10 @@ extern void RelationMapInitialize(void);
 extern void RelationMapInitializePhase2(void);
 extern void RelationMapInitializePhase3(void);
 
+extern Size EstimateRelationMapSpace(void);
+extern void SerializeRelationMap(Size maxSize, char *startAddress);
+extern void RestoreRelationMap(char *startAddress);
+
 extern void relmap_redo(XLogReaderState *record);
 extern void relmap_desc(StringInfo buf, XLogReaderState *record);
 extern const char *relmap_identify(uint8 info);