diff --git a/CHANGELOG_PENDING.md b/CHANGELOG_PENDING.md
index f4a10102f..a1a121164 100644
--- a/CHANGELOG_PENDING.md
+++ b/CHANGELOG_PENDING.md
@@ -20,6 +20,7 @@ program](https://hackerone.com/tendermint).
 
 ### IMPROVEMENTS:
 
+- [mempool] [\#4057](https://github.com/tendermint/tendermint/issues/4057) Include peer ID when logging rejected txns (@erikgrinaker)
 - [tools] [\#4023](https://github.com/tendermint/tendermint/issues/4023) Improved `tm-monitor` formatting of start time and avg tx throughput (@erikgrinaker)
 
 ### BUG FIXES:
diff --git a/mempool/clist_mempool.go b/mempool/clist_mempool.go
index 554839f1a..50a37e5aa 100644
--- a/mempool/clist_mempool.go
+++ b/mempool/clist_mempool.go
@@ -17,6 +17,7 @@ import (
 	"github.com/tendermint/tendermint/libs/clist"
 	cmn "github.com/tendermint/tendermint/libs/common"
 	"github.com/tendermint/tendermint/libs/log"
+	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/proxy"
 	"github.com/tendermint/tendermint/types"
 )
@@ -281,7 +282,7 @@ func (mem *CListMempool) CheckTxWithInfo(tx types.Tx, cb func(*abci.Response), t
 	}
 
 	reqRes := mem.proxyAppConn.CheckTxAsync(abci.RequestCheckTx{Tx: tx})
-	reqRes.SetCallback(mem.reqResCb(tx, txInfo.SenderID, cb))
+	reqRes.SetCallback(mem.reqResCb(tx, txInfo.SenderID, txInfo.SenderP2PID, cb))
 
 	return nil
 }
@@ -314,14 +315,19 @@ func (mem *CListMempool) globalCb(req *abci.Request, res *abci.Response) {
 // when all other response processing is complete.
 //
 // Used in CheckTxWithInfo to record PeerID who sent us the tx.
-func (mem *CListMempool) reqResCb(tx []byte, peerID uint16, externalCb func(*abci.Response)) func(res *abci.Response) {
+func (mem *CListMempool) reqResCb(
+	tx []byte,
+	peerID uint16,
+	peerP2PID p2p.ID,
+	externalCb func(*abci.Response),
+) func(res *abci.Response) {
 	return func(res *abci.Response) {
 		if mem.recheckCursor != nil {
 			// this should never happen
 			panic("recheck cursor is not nil in reqResCb")
 		}
 
-		mem.resCbFirstTime(tx, peerID, res)
+		mem.resCbFirstTime(tx, peerID, peerP2PID, res)
 
 		// update metrics
 		mem.metrics.Size.Set(float64(mem.Size()))
@@ -360,7 +366,12 @@ func (mem *CListMempool) removeTx(tx types.Tx, elem *clist.CElement, removeFromC
 //
 // The case where the app checks the tx for the second and subsequent times is
 // handled by the resCbRecheck callback.
-func (mem *CListMempool) resCbFirstTime(tx []byte, peerID uint16, res *abci.Response) {
+func (mem *CListMempool) resCbFirstTime(
+	tx []byte,
+	peerID uint16,
+	peerP2PID p2p.ID,
+	res *abci.Response,
+) {
 	switch r := res.Value.(type) {
 	case *abci.Response_CheckTx:
 		var postCheckErr error
@@ -384,7 +395,8 @@ func (mem *CListMempool) resCbFirstTime(tx []byte, peerID uint16, res *abci.Resp
 			mem.notifyTxsAvailable()
 		} else {
 			// ignore bad transaction
-			mem.logger.Info("Rejected bad transaction", "tx", txID(tx), "res", r, "err", postCheckErr)
+			mem.logger.Info("Rejected bad transaction",
+				"tx", txID(tx), "peerID", peerP2PID, "res", r, "err", postCheckErr)
 			mem.metrics.FailedTxs.Add(1)
 			// remove from cache (it might be good later)
 			mem.cache.Remove(tx)
diff --git a/mempool/mempool.go b/mempool/mempool.go
index 0995c734f..a979515ef 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	abci "github.com/tendermint/tendermint/abci/types"
+	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/types"
 )
 
@@ -90,9 +91,11 @@ type PostCheckFunc func(types.Tx, *abci.ResponseCheckTx) error
 // TxInfo are parameters that get passed when attempting to add a tx to the
 // mempool.
 type TxInfo struct {
-	// We don't use p2p.ID here because it's too big. The gain is to store max 2
-	// bytes with each tx to identify the sender rather than 20 bytes.
+	// SenderID is the internal peer ID used in the mempool to identify the
+	// sender, storing 2 bytes with each tx instead of 20 bytes for the p2p.ID.
 	SenderID uint16
+	// SenderP2PID is the actual p2p.ID of the sender, used e.g. for logging.
+	SenderP2PID p2p.ID
 }
 
 //--------------------------------------------------------------------------------
diff --git a/mempool/reactor.go b/mempool/reactor.go
index 349ed7ea5..35797b6c5 100644
--- a/mempool/reactor.go
+++ b/mempool/reactor.go
@@ -165,8 +165,11 @@ func (memR *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 
 	switch msg := msg.(type) {
 	case *TxMessage:
-		peerID := memR.ids.GetForPeer(src)
-		err := memR.mempool.CheckTxWithInfo(msg.Tx, nil, TxInfo{SenderID: peerID})
+		txInfo := TxInfo{SenderID: memR.ids.GetForPeer(src)}
+		if src != nil {
+			txInfo.SenderP2PID = src.ID()
+		}
+		err := memR.mempool.CheckTxWithInfo(msg.Tx, nil, txInfo)
 		if err != nil {
 			memR.Logger.Info("Could not check tx", "tx", txID(msg.Tx), "err", err)
 		}