Such was Mariner's impact that six months after joining Ipswich, he made his England debut as a substitute in a 5–0 win over Luxembourg at Wembley and played from the beginning in the following game against Northern Ireland in the British Home Championship at Windsor Park, Belfast. He impressed in both games, though did not score and was not selected for the next six matches. During this period, Ipswich finished third in the First Division, with Mariner contributing ten goals from 28 games.