Friday's triumph means that Leicester will be promoted if QPR lose at Bournemouth and Derby County fail to beat Middlesbrough this weekend.
While promotion and the title looks all but confirmed, Nigel Pearson's side were made to work hard for their 27th league win of the season.
Michail Antonio's 20-yard effort cancelled out Riyad Mahrez's early goal for the visitors, but Anthony Knockaert's 61st-minute free-kick proved the difference between the two sides.
Mahrez gave Leicester an early lead with his third league goal of the season, an excellent finish that capped a fast break.
The Frenchman cut inside onto his left foot, leaving Wednesday defender Joe Mattock stranded, before curling past goalkeeper Chris Kirkland from 15 yards.
David Nugent shot just wide when presented with a good chance in the 30th minute and he was made to rue his missed chance when Antonio scored from 20 yards.
Antonio beat Ritchie de Laet before shooting at Kasper Schmeichel, and the goalkeeper could only palm the effort into the back of the net.
He would make up for his error later in the piece but first Knockaert restored his side's advantage.
The French midfielder curled a 20-yard effort into the top left corner with Kirkland left flapping at the effort.
Wednesday pressed for an equaliser – and came close when the ball fell to Kieran Lee in stoppage time – but Schmeichel made a good reaction save to ensure his side emerged victorious.
