Goals from home debutants Brennan Dickenson and Denny Johnstone gave Colchester a deserved 2-0 win over Cambridge.
Colchester started well and made their breakthrough in the eighth minute - Chris Porter and Sammie Szmodics pouncing on goalkeeper Will Norris' poor clearance before Dickenson unleashed a low, left-footed shot that flew into the far corner.
The hosts almost doubled their lead two minutes later when Norris superbly tipped Szmodics' swerving 20-yard effort over for a corner, while Colchester keeper Sam Walker pulled off a magnificent save to foil Cambridge striker Joe Pigott soon after.
Leon Legge almost diverted Porter's low cross into his own net in the opening minutes of the second half but substitute Medy Elito came close to equalising against his former club when his free header clipped the top of the crossbar.
Norris parried away Porter's fierce effort before substitute Johnstone headed in Dickenson's cross from close range with eight minutes remaining, as Colchester claimed their first win of the season.