Last season’s beaten play-off finalists suffered a shock 1-0 home defeat to promoted Bristol City last weekend but ensured there was no repeat at Hillsborough to move onto eight points for the season.
Adam Reach put Boro in front in the closing stages of the first half and, although Marco Matias equalised just after the hour, Diego Fabbrini restored the visitors’ advantage almost immediately before substitute Christian Stuani added a third late on.
The defeat leaves Wednesday with just one win from their five league games this season, although they will soon be able to call on the services of striker Fernando Forestieri, whose signing on a four-year contract from Watford was announced shortly before kick-off.
There was more promising news for the home fans at the start of the game when, in the opening minutes, Lucas Joao found some space in the penalty area and it needed an important block from Daniel Ayala to deny him what could have been the opener.
Boro, who needed extra-time to overcome Burton in the Capital One Cup in midweek, responded with a shot from Stewart Downing which went wide after the England winger’s initial free-kick had struck the wall.
Wednesday keeper Lewis Price then came to his side’s rescue, tipping the ball over from Ayala’s header following a cross from Adam Clayton.
Joao received treatment following a crunching challenge from Ben Gibson which resulted in the Boro man received a yellow card just before the half-hour.
After being given the all-clear to continue, Joao’s low shot was partially blocked by a defender, which took the sting out of it, allowing keeper Dimitrios Konstantopoulos to make an easy save.
Price was called on to make another good save from Reach’s low drive as Boro threatened on the break.
Reach made no mistake with his next chance though to put Boro ahead in the 42nd minute, the midfielder drilling a low shot into the net from around eight yards out after Wednesday had failed to clear a Grant Leadbitter corner.
Wednesday had a chance to equalise before the interval with a Ross Wallace free-kick which went narrowly wide, and the hosts twice came close to levelling at the start of the second half through Alex Lopez.
He first saw a low shot fly inches wide of the keeper’s right-hand post before then floating a free-kick over the defensive wall which forced Konstantopoulos into a save to his right.
Wednesday’s improved showing paid off when Matias equalised with in the 64th minute with a deflected shot.
However, the hosts were only level for three minutes before Boro re-took the lead. Fabbrini was sent clear by David Nugent and the Italian advanced into the area before slotting past the exposed Price.
Wednesday tried to hit back and skipper Tom Lees headed just wide after meeting a corner from Kieran Lee and then the ball almost found its way to Lee inside the area when a Atdhe Nuhiu shot was blocked.
The Owls could not find a second equaliser though, and Stuani rounded off the scoring four minutes from time with a low shot after breaking free on the right-hand side of the area.
That sealed the win but Boro almost added a fourth goal in stoppage time when Adam Forshaw’s header which came back off a post.