The Scottish forward helped his side bounce back from consecutive defeats by sending visiting goalkeeper Joe Lewis the wrong way from the spot in the 39th minute after Peter Clarke was adjudged to have fouled Stevie May.
Bottom-of-the-table Blackpool had chances to grab a point but Ishmael Miller wasted a golden chance from close range before he was sent off in the fifth minute of injury time for two bookable offences.
Maguire hit the roof of the net with a 25-yard free-kick in the second minute before his strike partner May latched on to Royston Drenthe’s through-ball and lifted the ball over after being closed down by the onrushing Lewis.
Lee Clark’s side responded and winger Jacob Murphy curled narrowly wide of the right post from the left-hand corner of Wednesday’s 18-yard box.
Maguire lashed a 20-yard effort straight at Lewis midway through the half before Murphy’s shot from a similar distance at the other end was comfortably dealt with by Owls keeper Keiren Westwood.
Maguire then broke the deadlock, firing into the right corner to claim his first goal since the beginning of October following Clarke’s foul.
Blackpool’s Chris Eagles, a former Owls loanee, almost restored parity within a minute but, after breaking free on the left, the winger’s powerful strike flashed marginally wide with Westwood beaten.
Blackpool substitute Nathan Delfouneso, a first-half replacement for Steven Davies, saw his curling effort from 15 yards palmed away by the diving Westwood in the opening minute of the second period.
The Owls went close to doubling their advantage in the 50th minute when Maguire’s low cross from the left deflected off a Blackpool defender and looped on to Lewis’ crossbar.
Wednesday midfielder Lewis McGugan went through on goal four minutes later following a neat interchange between Drenthe and May, but Lewis was alert to smother the ball at the feet of the on-loan Watford man.
Dutchman Drenthe then smashed a dipping left-foot shot inches over from 20 yards before Blackpool striker Miller was booked for turning Tony McMahon’s centre into the Wednesday goal with a hand.
Scotland international May headed Drenthe’s cross towards goal in the 69th minute, only to be denied by a superb stop from visiting keeper Lewis.
Lewis’ opposite number Westwood then went one better, somehow repelling Miller’s three-yard header before the ball was hacked clear.
Blackpool, who remain 10 points adrift of safety and have failed to win away all season, saw their day go from bad to worse in the final moments when Miller was shown a second yellow card following a late tackle on defender Tom Lees.