diff --git a/conn.go b/conn.go
index d564326c..b0f2cac0 100644
--- a/conn.go
+++ b/conn.go
@@ -741,9 +741,9 @@ func (c *Conn) sendPreparedQuery(ps *PreparedStatement, arguments ...interface{}
 			wbuf.WriteInt16(TextFormatCode)
 		default:
 			switch oid {
-			case BoolOid, ByteaOid, Int2Oid, Int4Oid, Int8Oid, Float4Oid, Float8Oid:
+			case BoolOid, ByteaOid, Int2Oid, Int4Oid, Int8Oid, Float4Oid, Float8Oid, TimestampTzOid:
 				wbuf.WriteInt16(BinaryFormatCode)
-			case TextOid, VarcharOid, DateOid, TimestampTzOid:
+			case TextOid, VarcharOid, DateOid:
 				wbuf.WriteInt16(TextFormatCode)
 			default:
 				return SerializationError(fmt.Sprintf("Parameter %d oid %d is not a core type and argument type %T does not implement TextEncoder or BinaryEncoder", i, oid, arg))
diff --git a/values.go b/values.go
index d4af61eb..ea86556f 100644
--- a/values.go
+++ b/values.go
@@ -324,6 +324,45 @@ func (n NullBool) EncodeBinary(w *WriteBuf) error {
 	return encodeBool(w, n.Bool)
 }
 
+// NullTime represents an bigint that may be null.
+// NullTime implements the Scanner, TextEncoder, and BinaryEncoder interfaces
+// so it may be used both as an argument to Query[Row] and a destination for
+// Scan for prepared and unprepared queries.
+//
+// If Valid is false then the value is NULL.
+type NullTime struct {
+	Time  time.Time
+	Valid bool // Valid is true if Time is not NULL
+}
+
+func (n *NullTime) Scan(rows *Rows, fd *FieldDescription, size int32) error {
+	if size == -1 {
+		n.Time, n.Valid = time.Time{}, false
+		return nil
+	}
+	n.Valid = true
+	n.Time = decodeTimestampTz(rows, fd, size)
+
+	return rows.Err()
+}
+
+func (n NullTime) EncodeText() (string, byte, error) {
+	if n.Valid {
+		return n.Time.Format("2006-01-02 15:04:05.999999 -0700"), UnsafeText, nil
+	} else {
+		return "", NullText, nil
+	}
+}
+
+func (n NullTime) EncodeBinary(w *WriteBuf) error {
+	if !n.Valid {
+		w.WriteInt32(-1)
+		return nil
+	}
+
+	return encodeTimestampTz(w, n.Time)
+}
+
 var literalPattern *regexp.Regexp = regexp.MustCompile(`\$\d+`)
 
 // QuoteString escapes and quotes a string making it safe for interpolation
@@ -843,6 +882,8 @@ func encodeDate(w *WriteBuf, value interface{}) error {
 	return encodeText(w, s)
 }
 
+const microsecFromUnixEpochToY2K = 946684800 * 1000000
+
 func decodeTimestampTz(rows *Rows, fd *FieldDescription, size int32) time.Time {
 	var zeroTime time.Time
 
@@ -864,7 +905,6 @@ func decodeTimestampTz(rows *Rows, fd *FieldDescription, size int32) time.Time {
 		if size != 8 {
 			rows.Fatal(ProtocolError(fmt.Sprintf("Received an invalid size for an timestamptz: %d", size)))
 		}
-		microsecFromUnixEpochToY2K := int64(946684800 * 1000000)
 		microsecSinceY2K := rows.mr.ReadInt64()
 		microsecSinceUnixEpoch := microsecFromUnixEpochToY2K + microsecSinceY2K
 		return time.Unix(microsecSinceUnixEpoch/1000000, (microsecSinceUnixEpoch%1000000)*1000)
@@ -880,6 +920,11 @@ func encodeTimestampTz(w *WriteBuf, value interface{}) error {
 		return fmt.Errorf("Expected time.Time, received %T", value)
 	}
 
-	s := t.Format("2006-01-02 15:04:05.999999 -0700")
-	return encodeText(w, s)
+	microsecSinceUnixEpoch := t.Unix()*1000000 + int64(t.Nanosecond())/1000
+	microsecSinceY2K := microsecSinceUnixEpoch - microsecFromUnixEpochToY2K
+
+	w.WriteInt32(8)
+	w.WriteInt64(microsecSinceY2K)
+
+	return nil
 }
diff --git a/values_test.go b/values_test.go
index aa2151c1..0c208836 100644
--- a/values_test.go
+++ b/values_test.go
@@ -201,6 +201,7 @@ func TestNullX(t *testing.T) {
 		f32 pgx.NullFloat32
 		f64 pgx.NullFloat64
 		b   pgx.NullBool
+		t   pgx.NullTime
 	}
 
 	var actual, zero allTypes
@@ -225,6 +226,8 @@ func TestNullX(t *testing.T) {
 		{"select $1::float8", []interface{}{pgx.NullFloat64{Float64: 1.23, Valid: false}}, []interface{}{&actual.f64}, allTypes{f64: pgx.NullFloat64{Float64: 0, Valid: false}}},
 		{"select $1::bool", []interface{}{pgx.NullBool{Bool: true, Valid: true}}, []interface{}{&actual.b}, allTypes{b: pgx.NullBool{Bool: true, Valid: true}}},
 		{"select $1::bool", []interface{}{pgx.NullBool{Bool: true, Valid: false}}, []interface{}{&actual.b}, allTypes{b: pgx.NullBool{Bool: false, Valid: false}}},
+		{"select $1::timestamptz", []interface{}{pgx.NullTime{Time: time.Unix(123, 5000), Valid: true}}, []interface{}{&actual.t}, allTypes{t: pgx.NullTime{Time: time.Unix(123, 5000), Valid: true}}},
+		{"select $1::timestamptz", []interface{}{pgx.NullTime{Time: time.Unix(123, 5000), Valid: false}}, []interface{}{&actual.b}, allTypes{t: pgx.NullTime{Time: time.Time{}, Valid: false}}},
 	}
 
 	for i, tt := range tests {