diff --git a/pgconn/pgconn.go b/pgconn/pgconn.go
index 52577bb0..3d583dca 100644
--- a/pgconn/pgconn.go
+++ b/pgconn/pgconn.go
@@ -11,6 +11,7 @@ import (
 	"io"
 	"math"
 	"net"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -44,7 +45,8 @@ type Notification struct {
 // DialFunc is a function that can be used to connect to a PostgreSQL server.
 type DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
 
-// LookupFunc is a function that can be used to lookup IPs addrs from host.
+// LookupFunc is a function that can be used to lookup IPs addrs from host. Optionally an ip:port combination can be
+// returned in order to override the connection string's port.
 type LookupFunc func(ctx context.Context, host string) (addrs []string, err error)
 
 // BuildFrontendFunc is a function that can be used to create Frontend implementation for connection.
@@ -196,11 +198,24 @@ func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*Fallba
 		}
 
 		for _, ip := range ips {
-			configs = append(configs, &FallbackConfig{
-				Host:      ip,
-				Port:      fb.Port,
-				TLSConfig: fb.TLSConfig,
-			})
+			splitIP, splitPort, err := net.SplitHostPort(ip)
+			if err == nil {
+				port, err := strconv.ParseUint(splitPort, 10, 16)
+				if err != nil {
+					return nil, fmt.Errorf("error parsing port (%s) from lookup: %w", splitPort, err)
+				}
+				configs = append(configs, &FallbackConfig{
+					Host:      splitIP,
+					Port:      uint16(port),
+					TLSConfig: fb.TLSConfig,
+				})
+			} else {
+				configs = append(configs, &FallbackConfig{
+					Host:      ip,
+					Port:      fb.Port,
+					TLSConfig: fb.TLSConfig,
+				})
+			}
 		}
 	}
 
diff --git a/pgconn/pgconn_test.go b/pgconn/pgconn_test.go
index 22f0c26f..4350452c 100644
--- a/pgconn/pgconn_test.go
+++ b/pgconn/pgconn_test.go
@@ -237,6 +237,40 @@ func TestConnectCustomLookup(t *testing.T) {
 	closeConn(t, conn)
 }
 
+func TestConnectCustomLookupWithPort(t *testing.T) {
+	t.Parallel()
+
+	connString := os.Getenv("PGX_TEST_TCP_CONN_STRING")
+	if connString == "" {
+		t.Skipf("Skipping due to missing environment variable %v", "PGX_TEST_TCP_CONN_STRING")
+	}
+
+	config, err := pgconn.ParseConfig(connString)
+	require.NoError(t, err)
+
+	origPort := config.Port
+	// Chnage the config an invalid port so it will fail if used
+	config.Port = 0
+
+	looked := false
+	config.LookupFunc = func(ctx context.Context, host string) ([]string, error) {
+		looked = true
+		addrs, err := net.LookupHost(host)
+		if err != nil {
+			return nil, err
+		}
+		for i := range addrs {
+			addrs[i] = net.JoinHostPort(addrs[i], strconv.FormatUint(uint64(origPort), 10))
+		}
+		return addrs, nil
+	}
+
+	conn, err := pgconn.ConnectConfig(context.Background(), config)
+	require.NoError(t, err)
+	require.True(t, looked)
+	closeConn(t, conn)
+}
+
 func TestConnectWithRuntimeParams(t *testing.T) {
 	t.Parallel()