Dickson has impressed for the U's during pre-season following his release by Southampton this summer.
The 26-year-old told the club's official website: "t's good to be settled now and I've been happy since I first turned up here. There's a good squad here, the right philosophy in the way to play and a great work rate from all of the lads.
"The style of play is a good one to be involved in, the style suits me as a player and I've fitted in really well with the lads.
"Last year was a frustrating one for me so I am ready to get back to my top form and help Colchester push on because I think we've got a good chance with some real talented players here."
Dickson began his career with home-town club Plymouth before joining Brentford, where he played 87 times over two years.
He moved to Southampton in the summer of 2010 and helped Saints win promotion from League One in his first season with the south coast club. He has enjoyed loan spells with Yeovil, Leyton Orient and Bradford.