Mansfield's seven-match unbeaten run in League Two came to an end as second-half goals from substitutes Joe McNerney and Ibrahim Meite secured a 2-0 win for Crawley.
Steve Evans had not seen his side lose since October but the run came to an end against his former club.
McNerney scored after 63 minutes before Meite added a second in stoppage time to earn the Reds just a third home win under boss Harry Kewell.
Mansfield should have gone in front in only the second minute but a tame shot from CJ Hamilton was cleared off the line by Josh Yorwerth.
Crawley top-scorer Jordan Roberts drove over from 20 yards and was off target from the edge of the area before team-mate Enzio Boldewijn fired into the side netting.
After the interval Josh Payne put a free-kick over the crossbar and went closer soon after from long range.
Crawley broke the deadlock when Roberts crossed to the far post for half-time substitute McNerney, who headed in his first goal of the season.
Meiite sealed victory in the first minute of stoppage time, rounding goalkeeper Conrad Logan and scoring into an empty net.