The two promotion chasing sides could only be separated by a second half Sean Long header in a match which had very few clear cut chances.
Neither side was able to fully take a hold of the game but it was the Gloucestershire side who were able to just edge it on an evening heavily affected by the weather conditions.
Story of the match
Both sides came into the game looking to solidify their places in the automatic promotion spots, but it was the hosts who began to impose themselves in the early stages, enjoying much of the possession following the kick off.
Jack Iredale came agonisingly close to giving Cambridge the lead in the 17th minute when his in-swinging free kick was missed by everyone in the box before being acrobatically cleared off the line by George Lloyd.
The Us then again came close when Luke Hannant connected well with a half volley on the edge of the box in the 19th minute, bouncing just narrowly wide of the Cheltenham post.
Iredale then missed comfortably the best chance of the first half seeing his shot miraculously blocked on the line by Ben Tozer after getting around the goalkeeper in the 35th minute.
The Robins came out with greater intent following the break however, taking the lead in the 63rd minute when Long nodded home a dangerous cross from Alfie May.
United struggled to create clear cut chances in response coming closest to equalizing when top scorer Paul Mullin could only hit the side netting after after being played through from a ball from the deep in the 86th minute.
The victory for Michael Duffs side sees them move just two points behind their opponents, with Cambridge narrowly remaining top.
Man of the match - Sean Long
The Irishman was instrumental in a defence which manged to keep Mullin, league two's top scorer, very quiet.
The fullback also managed to be a consistent threat going forward in a game devoid of goal scoring opportunities.
His height created problems for the U's defence on a number of occasions, eventually leading up to his match winning goal.