Forest's unbeaten start to manager Billy Davies' second reign stretched to four games after an impressive victory at Hillsborough. The visitors were in control for much of the game and Majewski's 27th-minute goal did the damage, with the midfielder applying the simple finish after a fine run by Simon Cox.
The win ought to have been more comfortable as Cox, Majewski and Dexter Blackstock all had chances to extend the lead, but Davies' men had to settle for one. However, it was their third success in a row and leaves them four points shy of the play-offs going into the run-in.
For Wednesday, who rarely tested the Forest goal and put in a limp performance, it was the end of a seven-game unbeaten run, and despite their recent form they are still in a relegation dogfight, sitting just four points above the drop zone.
Henri Lansbury flashed a 25-yard effort just wide of Chris Kirkland's post early on and Andy Reid drifted a dangerous free-kick inches wide with Danny Collins just unable to make contact.
The visitors thought they were ahead in the 25th minute when Blackstock headed home, but he was adjudged to be offside.
Reid fed the striker and he went on a jinking run, ghosting past some non-existent defending before squaring for Majewski to slide home into an empty net.
It could have been even better for the visitors soon after as only a sublime intervention from Anthony Gardner prevented Cox from converting Reid's searching centre, before the Republic of Ireland frontman then dragged an effort wide.
Wednesday offered little by way of a response, much to the chagrin of a discontented home crowd, with Leroy Lita's tame effort from distance the only time Karl Darlow was called into action in the first half.
The second half was a similar affair with Forest controlling matters, although their final ball when in dangerous positions often let them down. Majewski did fashion a chance but dragged his shot wide from 16 yards while Blackstock could not make proper contact with a header from Cox's cross.
The Owls continued to look clueless in attack, although the whistle-blowing of referee Michael Oliver did little to appease a restless support - and they were further frustrated when Oliver opted not to award a penalty after the ball appeared to strike Jamaal Lascelles on the arm.
Dave Jones' men did at least pile the pressure on in the final 10 minutes, but Forest stood firm and marched to a third straight win.