Millwall's first-half opportunism gave them the points and handed Colchester a fourth successive home defeat.
Lewis Grabban intercepted David Perkins' sloppy pass to give the Lions the lead after nine minutes.
Paul Robinson then doubled the lead with a far-post header from Marc Laird's free-kick.
The U's responded with a close-range shot from Kem Izzet, who also hit the bar in the second half as Colchester failed to find the equaliser.
Colchester: Gerken, White, Reid, Baldwin, Jackson, Yeates, Hammond, Izzet (Elito 82), Perkins, Platt, Wasiu (Vernon 68). Subs Not Used: Cousins, Coyne, Wordsworth.
Booked: Hammond, White.
Goals: Izzet 35.
Please turn on JavaScript. Media requires JavaScript to play.
Booked: Laird, Hackett, Martin, Grabban.
Goals: Grabban 8, Robinson 22.
Att: 5,506
Ref: Grant Hegley (Hertfordshire).
What are these?
Print Sponsor
Bookmark with:
What are these?