It was the first away win in the Championship for Alex Neil's men this season, Maguire settling it from close range in the 23rd minute after Paul Gallagher's free-kick had come back off the post.
The pattern of the contest followed that of North End's previous away games this term, with them the better side in the first half before having to dig deep and show a lot of resilience in the second 45 minutes.
There were few chances all afternoon, Maguire showing a striker's instinct for the one which counted.
At times in the second half it wasn't pretty from a Preston perspective and Birmingham did have the ball in the net only to see the flag go up for offside.
But with Patrick Bauer and Ben Davies excellent at the heart of the defence, the visitors had enough in the tank to hold out against their hosts who didn't create much.
The North End side had shown four changes from the one which beat Brentford 2-0 last Saturday.
Ben Pearson returned from illness, with Andrew Hughes coming in for his first game since the second week of the season after being sidelined by hamstring trouble.
Gallagher and Josh Harrop came into the side, with Billy Bodin out injured while Alan Browne, Joe Rafferty and Ryan Ledson dropped to the bench.
PNE were in their usual 4-2-3-1 system, Tom Barkhuizen leading the attack, flanked by Maguire on the right and Harrop down the left.
There was precious little goalmouth action early on, Maguire having half a shout for a penalty when he went down under a challenge from Harlee Dean.
In fact the first real chance on goal saw North End take the lead in the 23rd minute.
Maguire was brought down by Dean on the edge of the 'D' to earn a free-kick.
Gallagher and Daniel Johnson stood over it, Gallagher being the one to step up and hit a low shot which beat the dive of keeper Lee Camp and struck the inside of the post.
The ball rolled across the six-yard box and Maguire was the first to react and side-foot home from close range.
Good defending by Hughes at the other end saw him stand-up to Maxime Colin and deflect his shot behind at the expense of a corner just before the half-hour mark.
In the 39th minute, referee Stephen Martin played the advantage when Maguire was tripped during a counter-attack, the ball running to Harrop who hit a shot from 25 yards, one which Camp got behind to save comfortably.
The opening spell of the second half was scrappy, the home side in the main on the attack with North End looking to counter.
Birmingham made a double change after an hour and one of those substitutes, Alvaro Gimenez, shot wide of the near post moments after coming on.
In the 65th minute, Darnell Fisher's throw-in found Harrop who checked inside from the right and squared a pass to Barkuizen, his scuffed shot rolling through to the keeper.
Referee Stephen Martin called a drinks' break at the 75-minute mark, taking into account how warm it was on the pitch.
Soon after the resumption in action, Gimenez swept the ball into the roof of the net from close range for Birmingham but the flag went up for offside against him.
More than eight minutes of injury-time were played for various stoppages, including a head injury for substitute Alan Browne.
North End saw it through to take the three points, the final whistle greeted by a huge cheer from the travelling 1,511 Preston supporters.
Birmingham: Camp, Colin, Roberts, Dean, Pedersen, Crowley, Davis (Villalba 79), Sunjic, Bellingham (Maghoma 61), Mrabti (Gimenez 61), Jutkiewicz. Subs (not used): Harding, Clarke-Salter, Gardner, Stockdale.
PNE: Rudd, Fisher (Rafferty 89), Bauer, Davies, Hughes, Pearson, Gallagher (Browne 82), Maguire, Johnson, Harrop, Barkhuizen (Potts 82). Subs (not used): Storey, Ledson, Stockley, Ripley.
Referee: Stephen Martin (Staffordshire)
Attendance: 20,806 (1,511 PNE)