Made captain for the day, Mackie passed up a golden opportunity to net his dream goal in the opening stages, but had to settle for a man-of-the-match display at a sun-baked Pittodrie.
His inclusion was one of three changes from the side that had drawn with Kilmarnock a week previously, with Russell Anderson and Jamie Langfield also returning to the starting eleven.
St Mirren could lift themselves to seventh with a win, and made one change from their defeat to Inverness Caledonian Thistle last week, with Graham Carey replacing Nigel Hasselbaink in the starting eleven
The Dons were on the front foot from the off, and should have been ahead within the first five minutes.
Andy Considine hit over from distance in the opening minute and a Jamie Masson cross had fizzed across goal just begging for a touch, before Mackie's first chance to notch a dream goal arrived.
Kari Arnason hit a superb pass in behind the St Mirren defence for Mackie to latch onto, but goalkeeper Craig Samson clearly had not read the script and got down to palm the striker's effort round the post.
Aberdeen were certainly looking the more likely, and should have punished an error by Samson after 14 minutes, the goalkeeper caught under Josh Magennis' long throw, but the ball scrambled clear.
Youngster Masson was impressing in the midfield, and a Mackie flick from his corner forced Jim Goodwin to clear off the line at the back post.
It took until the midway point of the first half for the visitors to register a shot on target, Stevie Thompson getting in behind Magennis before seeing his shot parried away by Langfield.
Heartened by the effort, they soon threatened again, Carey curling a 25-yard free-kick just inches wide of the post after Mark Reynolds had brought down Dougie Imrie.
Man-of-the-moment Mackie had another chance to sign off with a goal in front of the Dons support, before the half-hour, but this time flashed his close-range effort across the face of goal.
Considine became the first name to go into the book for a foul on Carey just outside the area just before the interval, but the former Celtic winger saw his effort comfortably held by Langfield.
As in the first half, the home side were quickly on the search for the opener in the second, and Masson should have done better with his header from Mackie's cross from the right.
Samson's goal was under threat again when the Buddies defence failed to deal with a free-kick from the left, clearing only as far as Gavin Rae who fizzed a left-foot volley over the crossbar from 20 yards.
Magennis followed team-mate Considine and St Mirren's Thompson into the book for a foul and, from the resultant free-kick, Thompson felt he was impeded, but his claim fell on deaf ears.
Thompson was in the wars again a minute later, his physical presence allowing him to flick towards the far post where Kenny McLean sent an acrobatic effort wide of the target.
In a bid to get a goal, Lennon threw on Hasselbaink and Gary Teale for Carey and Imrie just after the hour.
But Aberdeen still looked the more positive side, and when Reynolds found Scott Vernon in the area, it took a superb last-ditch tackle from Jeroen Tesselaar to deny the big Englishman.
The Dons' first change saw Rory McArdle, also set to depart the club in the summer, replace Magennis at right-back and Isaac Osbourne replaced Arnason shortly after.
A final Aberdeen sub saw the impressive Masson replaced by Ryan Fraser and the teenage winger immediately injected fresh life into the game, keen to take on his man at every opportunity.
Indeed, when Fraser was slipped in by Mackie just two minutes after coming on, his low cross was deflected toward goal forcing Samson to desperately palm away.
Marc McAusland was booked for a foul on Mackie, but at the other end, former Scotland striker Thompson came close again with a 12-yard strike, only denied by the legs of Langfield.
Ryan Jack had a final chance in injury time as he sent a 20-yard free-kick towards goal, but Samson saved comfortably.