On-the-whistle Owls report: Sheffield Wednesday 2Â Ipswich Town 1
The striker converted a header in each half to see off 10-man Ipswich Town 2-1 following Wednesday night's victory against Millwall by the same margin.
The Owls deserved the three points after taking control of a scrappy game in the second period against a Town side managed by boyhood Wednesday supporter Paul Hurst.
Their cause was helped by a straight red card for Aristote Nsiala for a challenge on substitute Fernando Forestieri minutes before Joao's match-winning second.
Jos Luhukay's side, who didn't win any of their opening three league matches, are now up to 13th in the table.
A slow beginning was quicky forgotten when Wednesday went ahead.
Joao needed only 16 minutes to score, pulling away from marker Trevoh Chalobah at the back post and heading home Barry Bannan's corner.
It was almost 2-0 four minutes later as Bannan's free-kick picked out Jordan Thorniley only for the young centre-half to power his header wide.
The Owls had a let-off when Jon Nolan was played clean through on the left but couldn't get the ball under control before Cameron Dawson spilled a routine catch from a Jonas Knudsen cross and had to be rescued by Thorniley.
They gave up their lead in 40th minute when Gwion Edwards' cross was flicked on to Nsiala who directed his header past Dawson in front of the kop.
The goalkeeper paid the price for not coming for a ball he might have claimed while boos rang out at Hillsborough from home supporters who thought the goal was offside.
The visitors finished a stop-start opening period on top, with Liam Palmer hurting himself in the process of producing a brave block on another Nsiala header and Ellis Harrison's shot bringing a smart save from Dawson.
Wednesday were faster out of the blocks after the break and Marco Matias wasted a golden opportunity to fire them in front six minutes into the second period.
The attacker was sent clear by Dawson's long kick but, with only the goalkeeper Bartosz Bialkowski to beat, he never had a bouncing ball truly under control and skewed his shot off target.
A minute later, Bannan, set up by Reach's run and pull-back, was thwarted by Knudsen's block a yard off the goalline and Joey Pelupessy fired the follow-up over.
Forestieri had just joined the action when referee Jeremy Simpson didn't like Nsiala's challenge and sent off the Ipswich scorer.
The breakthrough the home side's pressure merited came in the 77th minute and it was that man, Joao, on the scoresheet again.
His header from a corner hit the post but he made no mistake with his head at the second attempt as Atdhe Nuhiu followed in to make sure.
Good thinking by Nuhiu. Good work by Joao and the Owls.
Wednesday (4-3-3): Dawson; Palmer, Lees, Thorniley, Penney; Reach, Pelupessy, Bannan; Matias (Forestieri 73), Nuhiu, Joao (Fletcher 78). Subs not used: Wildsmith, Baker, Fox, Hutchinson, Kirby.
Ipswich (4-1-4-1): Bialkowski; Donacien, Nsiala, Chambers, Knudsen; Chalobah; Edwards, Edun (Downes 78), Nolan, Harrison (Sears 85); Jackson. Subs not used: Gerken, Spence, Ward, Roberts, Kenlock.
Goals: Joao 16, 77 (Wednesday); Nsiala 40 (Ipswich).
Referee: Jeremy Simpson (Lancashire).