He played 119 games for Northern Ireland as a goalkeeper, a figure which at the time was a world record and is still a Northern Ireland record, in an international career which lasted for over 22 years. During his career Jennings played for Newry Town, Watford, and in the top division with Tottenham Hotspur and Arsenal, winning the FA Cup with both of the north London rivals. In total, Jennings made over 1,000 top level appearances, and despite being a goalkeeper he scored in the 1967 FA Charity Shield.