diff --git a/pkg/sql/pgwire/command_result.go b/pkg/sql/pgwire/command_result.go
index ef6bfc17bca5..40c4ba19ce4e 100644
--- a/pkg/sql/pgwire/command_result.go
+++ b/pkg/sql/pgwire/command_result.go
@@ -161,11 +161,13 @@ func (r *commandResult) Close(ctx context.Context, t sql.TransactionStatusIndica
 		r.conn.bufferReadyForQuery(byte(t))
 		// The error is saved on conn.err.
 		_ /* err */ = r.conn.Flush(r.pos)
+		r.conn.maybeReallocate()
 	case emptyQueryResponse:
 		r.conn.bufferEmptyQueryResponse()
 	case flush:
 		// The error is saved on conn.err.
 		_ /* err */ = r.conn.Flush(r.pos)
+		r.conn.maybeReallocate()
 	case noCompletionMsg:
 		// nothing to do
 	default:
@@ -435,7 +437,7 @@ func (r *limitedCommandResult) AddRow(ctx context.Context, row tree.Datums) erro
 
 		return r.moreResultsNeeded(ctx)
 	}
-	return r.conn.maybeFlush(r.pos, r.bufferingDisabled)
+	return nil
 }
 
 // SupportsAddBatch is part of the sql.RestrictedCommandResult interface.
diff --git a/pkg/sql/pgwire/conn.go b/pkg/sql/pgwire/conn.go
index a50a722c9a4b..9b721fa10454 100644
--- a/pkg/sql/pgwire/conn.go
+++ b/pkg/sql/pgwire/conn.go
@@ -1593,12 +1593,30 @@ func (c *conn) Flush(pos sql.CmdPos) error {
 // maybeFlush flushes the buffer to the network connection if it exceeded
 // sessionArgs.ConnResultsBufferSize or if buffering is disabled.
 func (c *conn) maybeFlush(pos sql.CmdPos, bufferingDisabled bool) error {
+	// Note that ConnResultsBufferSize cannot be changed during a session, so it
+	// is safe to use the value stored on sessionArgs.
 	if !bufferingDisabled && int64(c.writerState.buf.Len()) <= c.sessionArgs.ConnResultsBufferSize {
 		return nil
 	}
 	return c.Flush(pos)
 }
 
+// maybeReallocate checks whether the internal slices used to buffer data have
+// overflowed their limits. If so, they will be reallocated to a smaller size.
+// maybeReallocate should only be called after the connection has been flushed
+// and a query has just been processed.
+func (c *conn) maybeReallocate() {
+	// Note that ConnResultsBufferSize cannot be changed during a session, so it
+	// is safe to use the value stored on sessionArgs.
+	limit := int(c.sessionArgs.ConnResultsBufferSize)
+	if c.msgBuilder.wrapped.Len() == 0 && c.msgBuilder.wrapped.Cap() > limit {
+		c.msgBuilder.wrapped = bytes.Buffer{}
+	}
+	if c.writerState.buf.Len() == 0 && c.writerState.buf.Cap() > limit {
+		c.writerState.buf = bytes.Buffer{}
+	}
+}
+
 // LockCommunication is part of the ClientComm interface.
 //
 // The current implementation of conn writes results to the network