Daniel Carey-Bertram was the hero as Cambridge came from behind to defeat bottom-of-the-table Southport.
The striker sent over a cross for David Bridges to head a 60th-minute equaliser before latching on to a Josh Simpson header to hit the winner soon after.
Southport had gone ahead in the 30th minute when Sean Doherty's cross found Tony Gray, whose looping header from 12 yards beat goalkeeper Paul Crichton.
Liam Blakeman then hit the bar from seven yards before Southport imploded.
606 DEBATE: Give your thoughts on the match
Southport: Robinson, Lane, Kirkup, Lee, Rowland, Donnelly (Baker 84), Boyd, Blakeman (Fowler 64), Doherty, Tait, Gray.
Subs Not Used: Harrison, Hoolickin, Powell.
Booked: Fowler, Lee.
Goals: Gray 30.
Cambridge Utd: Crichton, Bloomer, Peters, Morrison, Brown, Josh Simpson, Wolleaston, Bridges, Pitt, Richardson (Marum 75), Carey-Bertram.
Subs Not Used: Gash, Robbie Simpson, Quinton, Herbert.
Booked: Wolleaston, Josh Simpson, Bridges, Brown, Pitt.
Goals: Bridges 60, Carey-Bertram 64.
Ref: A Halliday (West Yorkshire).