It was a victory they had to work hard for as St Mirren dominated for long spells in the second half, but they deserved it on chances created.
It took a goal in each half from Rob Jones and then Derek Riordan to seal the points and send the Saints to their first defeat in six league matches.
Hibs had an early scare when Colin Nish headed out a free-kick straight into the path of Stephen McGinn, but Jones managed to get his head in the way.
Then Dennis Wyness tested Grzegorz Szamotulski with a low shot which the goalkeeper dealt with comfortably.
It provoked the desired response form Hibs - Riordan firing in a shot which Mark Howard could not hold and from Hibs' next raid, Riordan sent an ambitious effort high into the stands.
Nish then traded passes with Riordan, but again his long-range effort left a lot to be desired.
Steven Thicot brought a wonderful save from Howard with a 25-yard shot which the goalkeeper tipped over the top.
But from Riordan's corner, the goalkeeper was slow to react and Jones nipped in ahead of him to glance home a near-post header.
It was the first goal Saints had conceded in five matches and it was the early goal Hibs craved after their Scottish Cup exit.
A superb run from Lewis Stevenson from deep inside his own half to the edge of the Saints' penalty box almost brought a thrilling second goal, but he pulled his shot narrowly wide.
Riordan was then only inches away from a low cross played in intelligently by Nish, as Hibs looked well capable of snatching a second.
Hibs' confidence was evident when Sol Bamba fired in a shot from all of 35 yards which Howard did well to beat out.
Andy Dorman had a chance at the other end shortly before the break but his tame effort finished well wide.
The midfielder had a chance early in the second half after Bamba had given the ball away but his 20-yard shot was too high.
Scott Cuthbert thought he had equalised midway through the second half when he got his head to Garry Brady's corner, but Szamotulski somehow managed to fingertip the ball to safety.
Dorman then missed a better chance after 74 minutes when he had time in the area, but sent a wild shot over the top.
But Hibs sealed it six minutes from time when Riordan produced a brilliant right-foot finish from 16 yards after sub Ross Chisholm had put him through.