Black Cats debutant Ellis Simms scored twice, while Ross Stewart netted his first goal of the campaign by heading home the winner.
There were also a few surprises elsewhere on the second weekend of the season.
Here are some of the main stories.
1. Team performance of the weekend: Sheffield United
After an opening-day defeat at Watford, the Blades produced a comfortable 2-0 win over Millwall at Bramall Lane. Lions boss Gary Rowett felt there was a foul in the build-up to Iliman Ndiaye's opener, yet the hosts added a second through Sander Berge and could have scored a third when Oliver Norwood's penalty was saved. Photo: Cameron Smith
2. Individual performance of the weekend: Ellis Simms (Sunderland)
What a debut! The Everton loanee showed pace, strength and composure as he scored twice in Sunderland's 3-2 win at Bristol City. Simms, 21, could have bagged a hat-trick if it wasn't for an excellent save from goalkeeper Daniel Bentley. Photo: Ian Horrocks
3. Goal of the weekend: Chris Willock
Michael Beale claimed his first win as QPR boss as his side went 3-0 up inside 38 minutes against Middlesbrough. Willock opened the scoring with a stunning strike after a run from inside his own half, while Boro were unable to stage a late fightback in a 3-2 defeat. Photo: George Wood
4. A day to forget: Coventry
Coventry's home fixture against Rotherham had to be postponed after the pitch at the Coventry Building Society Arena was 'deemed unsafe and unplayable.' The club have apologised to frustrated supporters and said the fixture will be arranged in due course. Photo: Nathan Stirk