The U’s are still 23rd and two points adrift of safety, but Chris Porter’s late penalty gave them hope ahead of high-flying Preston’s visit next Sunday.
The visitors gradually began to dominate the action in the first period, but they were unable to find a way past Cod Army goalkeeper Chris Maxwell.
That changed after the restart, Jacob Murphy skipping past Nathan Pond and crossing from the left channel for George Moncur to scoop the ball home.
But the visitors could not sustain their tempo and it was two substitutes who helped Fleetwood pull level.
Josh Morris skipped into the box, finding David Ball, and he in turn picked out Jamie Proctor who, with his back to goal, turned and slotted low under Sam Walker.
Ball’s introduction turned the game on its head – the striker firing the hosts into the lead when he latched onto a through ball from Proctor, providing an ice-cool finish when one-on-one with Walker.
But Colchester were handed a lifeline by a goalkeeping clanger. When Gavin Massey shaped to cross, Maxwell completely misjudged the flight and let the ball slip under him and in.
Three minutes later the U’s were ahead again as Dion Sembie-Ferris charged into the box and tumbled under Pond’s clumsy challenge.
Porter converted from the spot, sparking a mini pitch invasion as Colchester sensed League One survival might be in their grasp after all.