Scott McGleish passed 100 goals in his career as his brace sunk Bristol City at Layer Road.
Front-runner McGleish scored twice within ten minutes in the second half to earn Colchester their first points of the new campaign.
The lively McGleish broke the deadlock on 47 minutes with what was his 100th League and Cup goal and it was a spectacular effort.
It all stemmed from a corner routine with Kem Izzet helping the ball on from Karl Duguid. But Izzet did not connect cleanly with his shot but the ball dropped invitingly for McGleish, who hit the target with a marvellous overhead kick.
And McGleish was soon celebrating his 101st goal with a series of somersaults when putting the U's two up in the 55th minute.
This time predator McGleish ghosted in at the near post to head home Duguid's free-kick, even though keeper Steve Phillips got his hands to the ball.
Bristol City certainly disappointed for the first hour, but they threatened a revival.
Manager Danny Wilson threw on three substitutes in the 62nd minute, and this resulted in a goal back within four minutes.
Substitute Christian Roberts won the free-kick, given away by Andy Myers, and fellow sub Brian Tinnion swung over the cross for striker Lee Peacock to nod home.
It was Peacock's sixth goal of the season and City were then denied an equaliser by the woodwork as Lee Matthews' shot hit a post on 70 minutes.
Yet the visitors did not really threaten again during the last 20 minutes, and five minutes of injury time, so suffering their first League defeat of the season.
The match was marred by no fewer than nine bookings, with referee Mr Cooper showing the yellow card to six City players and three home players.
Colchester hero Scott McGleish said: "We desperately wanted to get off the mark, and we finally managed it. Now we must keep this going at Tranmere on Saturday.
"It is nice to pass 100 goals in my career, but getting the right result was all important."