A goal after just four minutes from midfielder Jay Colbeck decided the points as the Reds confirmed their place in the play-offs for a third straight season.
The manager rang the changes with numerous new faces in the starting line-up to play the U's at the Racecourse. Choosing to rest some weary bones after a hectic Easter period.
There was a first start of the season for centre half Leon Clowes, while he was partnered by loanee David Artell, who had been previously unavailable due to a heel injury.
Both Jay Colbeck and Nick Rushton were also selected, while youngster Rob Evans was promoted from the youth team for a place on the bench.
The game got off to a great start as the new look Dragons swept forward at their guests and a sweeping move saw the decisive strike.
Declan Walker came down the right and his pass inside was taken by Colbeck in space on the edge of the box, the Scousers finding space to fire at goal, but keeper Nick Pope was equal to the effort, but Jay reacted quickly as the ball ran loose and crashed the ball home.
It was a lead that Wrexham were to maintain, as both sides looked for ways to score more goals.
Dele Adebola came close to another on 16 minutes when his shot across the United goal beat Pope but was a whisker wide of the far post.
Joe Clarke hand a drive that was not far from the mark and then Adebola hit an inviting cross on the break, that just evaded the foot of Walker at the back post who had made up some 80 yards to arrive a stride away from the ball.
At the interval there were three changes across the two teams, Wrexham making one of them and replacing the injured Kevin Thornton with Evans.
Cambridge almost pulled themselves level straight from the restart, as substitute Andy Pugh forced Chris Maxwell to come off his line, but the striker's attempted lob landed on the roof of the Wrexham net.
The lively Harrison Dunk was given a roving role for the U's and from the right produced an angled drive that the Wrexham keeper was able to parry away on 64 minutes.
The forward surges of Walker on the wing saw him combine with Adebola midway through the half and the striker was denied by a flying save from Pope to push away his effort from 15 yards.
Cambridge had little to lose at this stage and were committing men forward, enjoying periods of possession, as the Reds fell back on defence. Dunk seeing another effort, this time from the left rising over Maxwell's bar.
Coming on with just six minutes remaining, player boss Andy Morrell's first touch was to thread a ball through the United defence and it almost set up Brett Ormerod, but some good covering back denied the chance.
The new look Wrexham held firm at the back and referee Kevin Johnson brought a less then eventful match to a successful end for the home team.
Wrexham: Chris Maxwell, Declan Walker, Leon Clowes, David Artell, Neil Ashton; Adrian Cieslewicz">Adrian Cieslewicz (Brett Ormerod 71), Joe Clarke, Kevin Thornton (Rob Evans 46); Nick Rushton (Andy Morrell 84), James Colbeck, Dele Adebola.
Subs: Johnny Hunt, Danny Wright.
Cambridge United: Nicholas Pope, Kevin Roberts, Josh Coulson, Tom Shaw, Tom Elliott, Harrison Dunk, Rory McAuley, Rossi Jarvis (Luke Berry 66), Liam Hughes (Johnny Gorman 46), Charlie Wassmer, Sam Smith (Andy Pugh 46).
Subs: Nathan Blissett, Craig Ross.
Referee: Kevin Johnson (Somerset)