Tom Shaw's injury-time winner saw Cambridge United leapfrog visitors Woking into 11th in the table.
Kevin Betsy forced a good save from Cambridge's debutant keeper Nick Pope before Shaw drew Seb Brown into action at the other end.
Betsy missed a glorious opportunity and Jayden Stockley thought he deserved a penalty after a challenge by Kevin Roberts in the U's box.
And Shaw poked in Curtis Haynes-Brown's cross on 93 minutes to snatch the win.
VIEW FROM THE DRESSING ROOM
Woking manager Garry Hill told BBC Surrey:
"We probably thought we got the break right at the end when one of their defenders fouled Jayden Stockley and I cannot believe what I've seen.
"Why didn't he book the boy for diving? it was a very bad decision from the referee and he didn't have a lot to do today.
"But we got punished after that and we should have dealt with it, and I thought we should have got three points today, it hurts."