The young forward converted a crucial penalty five minutes from the end to eventually give his side a lead they struggled to get for so long.
And he poked home what proved to be the winner just moments later as Tommy Wilson’s men made it four wins from five matches in the competition so far.
Following his omission from the team that lost to Stirling on Saturday, Kyle Hutton was among the first-team players who featured.
Kevin Kyle was also involved along with fringe stars Robbie Crawford, Chris Hegarty, Andy Mitchell and Francesco Stella.
Gers had an early chance to go ahead through Kyle and should have taken it but they soon rued his weak shot at home keeper Andrew Duncan as they went two goals down instead.
Paul Di Giacomo gave the hosts the lead after eight minutes when he latched on to a through ball, got the better of makeshift left-back Mitchell and fired in from 10 yards.
Jack Boyle then doubled the advantage when he made the most of slack defending and nipped in to edge a trundling shot past Scott Gallacher.
Airdrie even came close to a third as the game hit the quarter-hour mark, with Di Giacomo so unlucky to see his rasping drive smack the face of the bar.
The away team soon responded and Stella put the ball in the net after good play by Crawford and Kyle but the Australian had just strayed offside and his effort didn’t stand.
Kyle had a header from a Naismith corner held by Duncan and put another on top of the net while Stella passed to the ex-Sunderland player when he should have had a go himself.
If anyone looked like getting the Ibrox outfit back into the contest before the break it was Naismith, whose creativity had Airdrie on the back foot at times.
He did really well to work his way into the area from the right corner and his shot was parried before Stella blasted the rebound high over the upright.
In general, the former Melbourne player was wasteful in front of goal and while he was getting into the right positions, he put one header past and drove a shot at the keeper.
That almost proved costly as Airdrie had one last chance before the interval but Gallacher was a match for Willie McLaren when he closed in on the target.
Coach Wilson retained his starting line-up for the restart but the home side continued to cause problems through the lively Di Giacomo.
And while chances kept coming for Rangers through Naismith’s long-range drive and Crawford’s shot on the turn, neither was on target and things weren’t going their way.
Hutton did hit the target on the hour after a disguised pass from Naismith but this time Duncan did well to stop the attempt then gather.
But just as frustration looked like setting in, Gers exerted more pressure on their opponents and finally got on the scoresheet on 63 minutes through Kamil Wiktorski.
He provided the finishing touch under Duncan from 10 yards after a smart pass in the box from Kyle and suddenly the away side was back in the game.
Rangers were visibly growing in confidence and both sides exchanged opportunities before the scores were levelled with eight minutes to go.
Mitchell came up with a composed finish as he ran on to a clever reverse pass by Naismith – but there was even more drama to come.
With five minutes left, Gers turned the game on its head as Crawford was fouled in the box and Naismith stepped up to stroke home a perfect penalty and make it 3-2.
The young forward then capped a good personal performance with a clincher barely 60 seconds later as he capped a terrific comeback with a confident finish.
Di Giacomo did have the final say with his second in injury time but it wouldn’t be enough to deny the Ibrox side.
Having been trailing with time running out, the Light Blues had dug deep to produce a winning result and keep their bid for the second-string title on course.
RANGERS: S Gallacher; Murdoch, Gasparotto, Hegarty, Mitchell; Hutton, Wiktorski; Naismith, Crawford, Stella (C Gallagher 54); Kyle.