In October 1961, Gemmell joined Celtic from Coltness United;[2] he signed youth terms on the same day as right winger Jimmy Johnstone, who lived a few miles away and would also have a long association with the club.

[4] Ironically, Gemmell should not have been in position to score the goal, as he had ignored team orders for one full-back to stay in defence at all times; the right back Jim Craig had already ventured forward, and it was he who played the square ball for Gemmell to shoot, with both advancing on the Inter box.

[7] Gemmell also scored in the 1970 European Cup final in a defeat to Feyenoord,[8][9] making him currently one of only three British footballers to score in two different European Cup finals, the others being Phil Neal of Liverpool and Gareth Bale of Real Madrid.

[3] He also stated that he received verbal abuse on several occasions from some supporters of Old Firm rivals Rangers due to his perceived status as a 'turncoat' (as a Protestant who played for Celtic), such as when attending matches many years after retiring.

He returned to Scotland, signing for Dundee in July 1973, and won the 1973 Scottish League Cup final against former team Celtic.

[18] The following year on 15 April, he played in the famous Home Championship match where Scotland recorded a 3–2 victory over World Champions England at Wembley Stadium, ending that team's run of nineteen games without defeat.

[19] He won 18 caps and scored one goal from the penalty spot against Cyprus in an 8–0 win in a 1970 World Cup qualifier.