diff --git a/consensus/common_test.go b/consensus/common_test.go
index ea1415924..55f4d5828 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -255,7 +255,7 @@ func newConsensusStateWithConfigAndBlockStore(thisConfig *cfg.Config, state sm.S
 	proxyAppConnCon := abcicli.NewLocalClient(mtx, app)
 
 	// Make Mempool
-	mempool := mempl.NewMempool(thisConfig.Mempool, proxyAppConnMem, 0)
+	mempool := mempl.NewMempool(thisConfig.Mempool, proxyAppConnMem, 0, mempl.NopMetrics())
 	mempool.SetLogger(log.TestingLogger().With("module", "mempool"))
 	if thisConfig.Consensus.WaitForTxs() {
 		mempool.EnableTxsAvailable()
diff --git a/mempool/mempool.go b/mempool/mempool.go
index 5af16b3c9..a1f9cd179 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -83,10 +83,12 @@ type Mempool struct {
 	wal *auto.AutoFile
 
 	logger log.Logger
+
+	metrics *Metrics
 }
 
 // NewMempool returns a new Mempool with the given configuration and connection to an application.
-func NewMempool(config *cfg.MempoolConfig, proxyAppConn proxy.AppConnMempool, height int64) *Mempool {
+func NewMempool(config *cfg.MempoolConfig, proxyAppConn proxy.AppConnMempool, height int64, metrics *Metrics) *Mempool {
 	mempool := &Mempool{
 		config:        config,
 		proxyAppConn:  proxyAppConn,
@@ -98,6 +100,7 @@ func NewMempool(config *cfg.MempoolConfig, proxyAppConn proxy.AppConnMempool, he
 		recheckEnd:    nil,
 		logger:        log.NewNopLogger(),
 		cache:         newTxCache(config.CacheSize),
+		metrics:       metrics,
 	}
 	proxyAppConn.SetResponseCallback(mempool.resCb)
 	return mempool
@@ -250,6 +253,7 @@ func (mem *Mempool) resCb(req *abci.Request, res *abci.Response) {
 	} else {
 		mem.resCbRecheck(req, res)
 	}
+	mem.metrics.Size.Set(float64(mem.Size()))
 }
 
 func (mem *Mempool) resCbNormal(req *abci.Request, res *abci.Response) {
@@ -393,6 +397,7 @@ func (mem *Mempool) Update(height int64, txs types.Txs) error {
 		// mem.recheckCursor re-scans mem.txs and possibly removes some txs.
 		// Before mem.Reap(), we should wait for mem.recheckCursor to be nil.
 	}
+	mem.metrics.Size.Set(float64(mem.Size()))
 	return nil
 }
 
diff --git a/mempool/mempool_test.go b/mempool/mempool_test.go
index a67adf6d3..45aa27a8b 100644
--- a/mempool/mempool_test.go
+++ b/mempool/mempool_test.go
@@ -33,7 +33,7 @@ func newMempoolWithApp(cc proxy.ClientCreator) *Mempool {
 	if err != nil {
 		panic(err)
 	}
-	mempool := NewMempool(config.Mempool, appConnMem, 0)
+	mempool := NewMempool(config.Mempool, appConnMem, 0, NopMetrics())
 	mempool.SetLogger(log.TestingLogger())
 	return mempool
 }
@@ -241,7 +241,7 @@ func TestMempoolCloseWAL(t *testing.T) {
 	app := kvstore.NewKVStoreApplication()
 	cc := proxy.NewLocalClientCreator(app)
 	appConnMem, _ := cc.NewABCIClient()
-	mempool := NewMempool(wcfg, appConnMem, 10)
+	mempool := NewMempool(wcfg, appConnMem, 10, NopMetrics())
 	mempool.InitWAL()
 
 	// 4. Ensure that the directory contains the WAL file
diff --git a/mempool/metrics.go b/mempool/metrics.go
new file mode 100644
index 000000000..3457285f3
--- /dev/null
+++ b/mempool/metrics.go
@@ -0,0 +1,17 @@
+package mempool
+
+import "github.com/go-kit/kit/metrics"
+import "github.com/go-kit/kit/metrics/discard"
+
+// Metrics contains metrics exposed by this package.
+// see MetricsProvider for descriptions.
+type Metrics struct {
+	Size metrics.Gauge
+}
+
+// NopMetrics returns no-op Metrics.
+func NopMetrics() *Metrics {
+	return &Metrics{
+		Size: discard.NewGauge(),
+	}
+}
diff --git a/node/node.go b/node/node.go
index a8671c9f8..acb3461b0 100644
--- a/node/node.go
+++ b/node/node.go
@@ -91,11 +91,11 @@ func DefaultNewNode(config *cfg.Config, logger log.Logger) (*Node, error) {
 }
 
 // MetricsProvider returns a consensus and p2p Metrics.
-type MetricsProvider func() (*cs.Metrics, *p2p.Metrics)
+type MetricsProvider func() (*cs.Metrics, *p2p.Metrics, *mempl.Metrics)
 
 // DefaultMetricsProvider returns a consensus and p2p Metrics build using
 // Prometheus client library.
-func DefaultMetricsProvider() (*cs.Metrics, *p2p.Metrics) {
+func DefaultMetricsProvider() (*cs.Metrics, *p2p.Metrics, *mempl.Metrics) {
 	return &cs.Metrics{
 			Height: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
 				Subsystem: "consensus",
@@ -167,6 +167,12 @@ func DefaultMetricsProvider() (*cs.Metrics, *p2p.Metrics) {
 				Name:      "peers",
 				Help:      "Number of peers.",
 			}, []string{}),
+		}, &mempl.Metrics{
+			Size: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
+				Subsystem: "mempool",
+				Name:      "size",
+				Help:      "Size of the mempool (number of uncommitted transactions).",
+			}, []string{}),
 		}
 }
 
@@ -294,9 +300,11 @@ func NewNode(config *cfg.Config,
 		consensusLogger.Info("This node is not a validator", "addr", privValidator.GetAddress(), "pubKey", privValidator.GetPubKey())
 	}
 
+	csMetrics, p2pMetrics, memplMetrics := metricsProvider()
+
 	// Make MempoolReactor
 	mempoolLogger := logger.With("module", "mempool")
-	mempool := mempl.NewMempool(config.Mempool, proxyApp.Mempool(), state.LastBlockHeight)
+	mempool := mempl.NewMempool(config.Mempool, proxyApp.Mempool(), state.LastBlockHeight, memplMetrics)
 	mempool.InitWAL() // no need to have the mempool wal during tests
 	mempool.SetLogger(mempoolLogger)
 	mempoolReactor := mempl.NewMempoolReactor(config.Mempool, mempool)
@@ -326,8 +334,6 @@ func NewNode(config *cfg.Config,
 	bcReactor := bc.NewBlockchainReactor(state.Copy(), blockExec, blockStore, fastSync)
 	bcReactor.SetLogger(logger.With("module", "blockchain"))
 
-	csMetrics, p2pMetrics := metricsProvider()
-
 	// Make ConsensusReactor
 	consensusState := cs.NewConsensusState(config.Consensus, state.Copy(),
 		blockExec, blockStore, mempool, evidencePool, csMetrics)