Etienne Esajas's deflected effort for Wednesday condemned bottom club Nottingham Forest to their fifth straight away defeat.
In a scrappy first half, the hosts were denied a penalty when Marcus Tudgay tangled with Kelvin Wilson and then saw Deon Burton wastefully head wide.
They finally went ahead on 48 minutes when Esajas' left-foot effort took a wicked deflection off Ian Breckin.
Andrew Cole had two good efforts saved but Forest could find no way back.
Sheffield Wednesday manager Brian Laws:
"It's nice to be where we are but there's 40-odd games to go. We just have to keep the momentum going and see where we are.
"It's a great start to the season and a complete role reversal to last season.
"There is a real belief in the camp and we've got to continue this run. We saw what happened with Bristol City last season."
Nottingham Forest manager Colin Calderwood:
"Frustration is growing, especially with the manner of the goals we have conceded in the last two games.
"But there were signs of improvement, we showed good character and I don't think there was much between the sides. Their keeper made some good saves, but we should have capitalised on our chances.
"At the moment we are finding it hard to get a victory, but we can't afford to feel sorry for ourselves."
Sheff Wed: Grant, Spurr, Gilbert, Wood (Beevers 64), McMahon, McAllister, Esajas, O'Connor, Small (Jeffers 76), Tudgay, Burton.
Subs Not Used: O'Donnell, Smith, Clarke.
Goals: Esajas 48.
Nottm Forest: Smith, Wilson, Breckin, Perch, Bennett (Martin 68), Lynch (Moussi 88), Chambers (McCleary 68), Cohen, Tyson, Cole, Thornhill.
Subs Not Used: Davies, Sinclair.
Att: 20,823.
Ref: Andy D'Urso (Essex).
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