The defending champions were Linfield, who defeated Ballymena United 3–1 in the 1977–78 final. However, they were knocked out by eventual winners Cliftonville in the first round. Cliftonville went on to win the cup for the 8th time, defeating Portadown 3–2 in the final. The 1979 victory represented their first cup success in 70 years; this remains a record for the longest gap between Irish Cup wins. To date, this is Cliftonville's last Irish Cup success, though they have reached the final five times since this win; in 1997, 1999, 2009 and 2013. They lost the 1997, 2009 and 2013 finals, and were disqualified before the final was played in 1999 when it was discovered that they had fielded an ineligible player in the earlier rounds.