diff --git a/doc/release-notes-15637.md b/doc/release-notes-15637.md
new file mode 100644
index 000000000..048d5e721
--- /dev/null
+++ b/doc/release-notes-15637.md
@@ -0,0 +1,3 @@
+RPC changes
+-----------
+In getmempoolancestors, getmempooldescendants, getmempoolentry and getrawmempool RPCs, to be consistent with the returned value and other RPCs such as getrawtransaction, vsize has been added and size is now deprecated. size will only be returned if bitcoind is started with `-deprecatedrpc=size`.
\ No newline at end of file
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 1827aec63..d35f458b2 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -378,7 +378,9 @@ static UniValue getdifficulty(const JSONRPCRequest& request)
 
 static std::string EntryDescriptionString()
 {
-    return "    \"size\" : n,             (numeric) virtual transaction size as defined in BIP 141. This is different from actual serialized size for witness transactions as witness data is discounted.\n"
+    return "    \"vsize\" : n,            (numeric) virtual transaction size as defined in BIP 141. This is different from actual serialized size for witness transactions as witness data is discounted.\n"
+           "    \"size\" : n,             (numeric) (DEPRECATED) same as vsize. Only returned if bitcoind is started with -deprecatedrpc=size\n"
+           "                              size will be completely removed in v0.20.\n"
            "    \"fee\" : n,              (numeric) transaction fee in " + CURRENCY_UNIT + " (DEPRECATED)\n"
            "    \"modifiedfee\" : n,      (numeric) transaction fee with fee deltas used for mining priority (DEPRECATED)\n"
            "    \"time\" : n,             (numeric) local time transaction entered pool in seconds since 1 Jan 1970 GMT\n"
@@ -416,7 +418,8 @@ static void entryToJSON(const CTxMemPool& pool, UniValue& info, const CTxMemPool
     fees.pushKV("descendant", ValueFromAmount(e.GetModFeesWithDescendants()));
     info.pushKV("fees", fees);
 
-    info.pushKV("size", (int)e.GetTxSize());
+    info.pushKV("vsize", (int)e.GetTxSize());
+    if (IsDeprecatedRPCEnabled("size")) info.pushKV("size", (int)e.GetTxSize());
     info.pushKV("fee", ValueFromAmount(e.GetFee()));
     info.pushKV("modifiedfee", ValueFromAmount(e.GetModifiedFee()));
     info.pushKV("time", e.GetTime());
diff --git a/test/functional/mempool_packages.py b/test/functional/mempool_packages.py
index 7cee215d5..507cdfa9f 100755
--- a/test/functional/mempool_packages.py
+++ b/test/functional/mempool_packages.py
@@ -58,9 +58,9 @@ class MempoolPackagesTest(BitcoinTestFramework):
         assert_equal(len(mempool), MAX_ANCESTORS)
         descendant_count = 1
         descendant_fees = 0
-        descendant_size = 0
+        descendant_vsize = 0
 
-        ancestor_size = sum([mempool[tx]['size'] for tx in mempool])
+        ancestor_vsize = sum([mempool[tx]['vsize'] for tx in mempool])
         ancestor_count = MAX_ANCESTORS
         ancestor_fees = sum([mempool[tx]['fee'] for tx in mempool])
 
@@ -79,15 +79,15 @@ class MempoolPackagesTest(BitcoinTestFramework):
             assert_equal(mempool[x]['fees']['modified'], mempool[x]['modifiedfee'])
             assert_equal(mempool[x]['descendantfees'], descendant_fees * COIN)
             assert_equal(mempool[x]['fees']['descendant'], descendant_fees)
-            descendant_size += mempool[x]['size']
-            assert_equal(mempool[x]['descendantsize'], descendant_size)
+            descendant_vsize += mempool[x]['vsize']
+            assert_equal(mempool[x]['descendantsize'], descendant_vsize)
             descendant_count += 1
 
             # Check that ancestor calculations are correct
             assert_equal(mempool[x]['ancestorcount'], ancestor_count)
             assert_equal(mempool[x]['ancestorfees'], ancestor_fees * COIN)
-            assert_equal(mempool[x]['ancestorsize'], ancestor_size)
-            ancestor_size -= mempool[x]['size']
+            assert_equal(mempool[x]['ancestorsize'], ancestor_vsize)
+            ancestor_vsize -= mempool[x]['vsize']
             ancestor_fees -= mempool[x]['fee']
             ancestor_count -= 1
 
diff --git a/test/functional/mining_prioritisetransaction.py b/test/functional/mining_prioritisetransaction.py
index 687a5b527..b0a069be8 100755
--- a/test/functional/mining_prioritisetransaction.py
+++ b/test/functional/mining_prioritisetransaction.py
@@ -64,7 +64,7 @@ class PrioritiseTransactionTest(BitcoinTestFramework):
         for i in range(3):
             for j in txids[i]:
                 assert j in mempool
-                sizes[i] += mempool[j]['size']
+                sizes[i] += mempool[j]['vsize']
             assert sizes[i] > MAX_BLOCK_BASE_SIZE  # Fail => raise utxo_count
 
         # add a fee delta to something in the cheapest bucket and make sure it gets mined