Born in Clontarf, Hanahoe excelled at both Gaelic football and hurling in his youth. He was educated at St. Joseph's Secondary School Fairview where he first developed his skills in both codes. Hanahoe joined the St. Vincent's club and, after progressing through the juvenile and underage grades, was a regular member of the starting fifteen by 1964. He won the first of eleven county senior championship medals that year, however, the highlight of his club career came in 1976 when he won an All-Ireland medal. Hanahoe also won three Leinster medals before retiring after a two-decade-long career.