Patsy was born in Ramelton where he learned to play football. As a school boy he played for his first team and had also to organize it. He was captain and secretary at the same time because every teacher in the school was female and showed little interest in the sport.

He was quickly promoted to the first team of Celtic where he played for 15 years from 1911 to 1926 and scored 192 goals. One of his most famous moments came in the 1925 Scottish Cup final, when he somersaulted over the goal line with the ball between his feet.

With Gallacher in the team Celtic won 7 League Championships, 4 Scottish Cups, 4 Glasgow Cups and
11 Glasgow Charity Cups.
In 1926, Celtic "retired" Patsy. It was presumed that they wanted to save on his wages.
He then went on to play with Falkirk for 6 more years.