McAndrew was named man of the match after SA tore through Victoria on the final morning, winning by 56 runs and claiming back-to-back titles for the first time.
Chasing 196 to win, Victoria lost the crucial wickets of former Test players Peter Handscomb and Marcus Harris with less than 20 minutes left on day four and never recovered.
From 3-102 late on Sunday, they were blasted out for 139 at Junction Oval - losing 5-37 on Monday morning - after dominating the competition this summer.
By contrast, SA struggled with injuries in their title defence and did not secure second spot until the last round.
But their struggles steeled their spines for an absorbing final, marked by frequent rain delays through the first three days and several plot twists.
One of the biggest turning points was before lunch on Sunday, when Test paceman Scott Boland was on a hat-trick and SA reeling in their second innings at 7-122.
McAndrew joined Test 'keeper Alex Carey at the crease and, by Victoria's estimations, the tailender played and missed 16 times.
"I looked like an absolute mug who could barely hit it off the square," was McAndrew's assessment.
But unlike the Vics in their disastrous run chase, he survived.
McAndrew scored 60 and shared in a 105-run stand with Carey for the eighth wicket that turned the game.
Carey top-scored with 103 and SA made 258, piling the pressure on the title favourites.
McAndrew was diagnosed last year with vestibular neuritis, a form of vertigo, and has had to overcome the debilitating symptoms to star for SA this summer.
Along with his half-century heroics, he also took six wickets in the final.
Coach Ryan Harris said the paceman should have been in the Test team already.
McAndrew was proud post game, but admitted to being banged up.
"I can't feel anything at the moment - the codeine just kicked in," he said.
"I feel like I'm bowling as well as I have at times, even with some of the challenges I've had this year, with the vertigo, and how much that affected my rhythm," he said.
"Since Christmas, I've gotten back to my best and I'm just really proud of that. It's been a pretty tough year with some things."
But given the strength of the Australian pace attack, McAndrew is under no illusions - "I'm not that stupid' - and added he would only be promoted because of an injury.
At 32, he only made his Shield debut for SA five years ago.
Harris said this title felt slightly more special than last season, given the adversity they have overcome.
"One of the things I've tried to instil is, whatever the scenario, we just have to fight," Harris said.
"You have to walk off that ground with your backside hanging out.
"Coaching for me last year was easy ... this year was bloody hard and that's what probably makes this a little more special."
Of all the key moments in the game, Harris felt the dismissals of Handscomb and Harris in successive overs were most important.
"To get two blokes who have played Test cricket, can bat a long time, on a nice wicket with a old ball, that was the turning point," he said.
Victoria coach Chris Rogers said this hurt more than losing earlier this decade to WA in successive seasons.
"We had a bit of a tricky chase and we just didn't have enough people who stood up," he said.
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