Colchester reached the FA Cup quarter-final, famously beating First Division Leeds United 3–2 at Layer Road in the fifth round.

During the summer of 1970, manager Dick Graham increased the average age of his Colchester squad by signing a number of ageing players, including ex-England international Ray Crawford, Brian Garvey, John Kurila, Mick Mahon and Brian Owen.

During the season, both Owen and Roy Massey suffered serious or career ending injuries, forcing Graham into signing Brian Lewis and Dave Simmons.

Dick Graham's Grandad's Army finally succumbed to defeated by a 5–0 scoreline in front of a crowd of 53,028.

With fixtures backing up, a run of 17 league games following their cup exit until the end of the season proved too much as they finished the campaign in sixth position, two points shy of promotion.