While the Cats have all but confirmed their finals berth, the Saints' loss leaves them with little hope of September action.
They will also be sweating on a second-term incident in which much-admired veteran Lenny Hayes connected with the head of Cats player Taylor Hunt after arriving late at a marking contest.
Geelong dominated the first half to lead by 34 points, with Hawkins kicking four first-half majors.
But the Saints controlled the third quarter and the early part of the last, scoring 5.8 to Geelong's 0.5 during that part of the game to cut the margin to just one point six minutes into the final term.
Fittingly, it was Hawkins who answered, roving the front of a goalsquare pack to kick his fifth goal of the night and the Cats' first of the second half to stem the Saints' momentum.
Youngster Jordan Murdoch and premiership veteran Andrew Mackie then converted 50m set shots five minutes apart to further stretch the buffer.
Hawkins, who had been in doubt early in the week after being concussed against West Coast last Friday night, then sealed the win with his sixth major after marking early in time-on, the Cats ramming home their advantage with three more goals.
Earlier, the Cats had controlled the game in general play.
Only some clever goals from small forwards Stephen Milne (four goals) and Ahmed Saad (three), a major from a fortunate 50m penalty and another from an off-the-ball free kick kept the Saints in striking range in the first half.
Their attack looked unthreatening in the absence of injured skipper Nick Riewoldt, fellow tall forward Justin Koschitzke failing to fire in his captain's absence, subbed off early in the third term with just one disposal.
But the Saints turned the midfield tables in third term to edge their way back into the contest.
If not for some bad missed chances in front of goal, the Saints kicking 3.7 for the quarter, they could have been closer than 13 points at the last change.
Even so, goals to Saad and substitute Adam Schneider early in the final term put them within a point before the Cats responded.
The second-quarter incident involving Hayes is sure to be scrutinised by the match review panel on Monday.
He arrived fractionally late after Hunt marked and crashed into the Cat, who had to leave the ground with a bloodied nose.
With the Saints unlikely to play finals and the midfield star yet to commit to playing on beyond this season, if he does cop a suspension of two or more matches it could potentially end his career.
St Kilda big man Rhys Stanley went to hospital during the last quarter with suspected rib or lung damage.