Kevin Heffernan had a distinguished career playing Gaelic football. He captained Dublin to All-Ireland victory in 1958, was in the winning National League winning teams of 1953, 1955 and 1958, and won seven Railway Cup medals with Leinster. He played for Dublin at minor, junior and senior levels in both hurling and football, and also helped, St Vincents, to win the County Championship in both codes. He won the All-Ireland Junior Football Championship with Dublin in 1948.

In spite of having a career as a player he will always be associated with the great Dublin football teams of the 1970s which he coached to All-Ireland successes in 1974, 1976, 1977, 1983 and to National League titles in 1976 and 1978. The era was dominated by Dublin's great rivalry with Keery former county's ecstatic fans dubbed "Heffo’s Army". In 1974 Heffernan became the only non-player to be nominated Texaco Footballer of the Year.

The 1974 Final win was memorable as Dublin had been out of the limelight for eleven years and were expectations of success were not high. In 1975 a young Kerry team caught Heffernan's Dubs in a complacent mood but Heffernan had his revenge in the All-Ireland Final of 1976. He masterminded another victory over Kerry in 1977 in what is often described by Football fans as the greatest game ever played. They easily accounted for Armagh in the Final that year.

Heffernan's retirement after this game shocked many and team captain Tony Hanahoe presided over a defeat in the Final of 1978. Heffernan returned in 1979 but again lost out to Kerry. Much of the team fell by the wayside after 1980 but Heffernan built a new team around midfield stalwart Brian Mullins and in another memorable match, remembered mainly for its unsporting conduct, 12 Dublin players beat 14 Galway players in the All-Ireland Final of 1983. Played in atrocious conditions the referee sent off 4 players, 3 from Dublin, and their win saw the team being dubbed "the twelve apostles".

Following his retirement from Inter-County management, Heffernan continued to manage teams and win Dublin County Championships with St. Vincents. In 2004, at the age of 74 he was in charge of the club's Under 15 hurling team, which, with a late free from Oliver McElvaney, won a memorable championship final against Cuala, having defeated Ballyboden in the semi final. This particular St. Vincents team had never beaten either of those two clubs before, illustrating to all that Heffernan's management touch had not deserted him. In 2006 he will train the club's minor (U/18) hurling team.

By profession Heffernan was a personnel manager for the Electricity Supply Board (ESB) and he became Chairman of the Labour Court.

In 2005 he was granted the Freedom of the City of Dublin, placing him in a pantheon that includes U2, Nelson Mandela and Bill Clinton.

Kevin Heffernan was among the 25 recipients of the Irish Examiner GAA President's Awards for 2006. The ceremony which was presented by the former GAA president Seán Kelly , took place on the Friday, 31 March 2006.

Heffernan was named left corner forward on the GAA Gaelic Football Team of the Millennium.