Patrick Bamford scored both goals for Marcelo Bielsa's men in a 2-0 victory away to Wigan Athletic, which had Joe Williams sent off in the 21st minute.
Sheffield Wednesday enjoyed a numerical advantage for over 45 minutes in its match at Millwall but failed to muster a response to Matt Smith's first-half effort.
That result, coupled with Charlton Athletic's draw against Barnsley, opened the door to the Whites and means no team can boast a perfect record after three matches.
Two tap-ins from former Chelsea forward Bamford helped Leeds exact a measure of revenge on Wigan at DW Stadium.
The Latics derailed the Yorkshire club's promotion push last season when, with 10 men, they came from behind to claim a shock 2-1 win at Elland Road.
There was no repeat this time as the dismissal of midfielder Williams for two bookable offences only left the home side's defence prone to a pair of close-range Bamford finishes.
The goals arrived either side of half-time and improved the 25-year-old's season tally to three in as many matches.
Wednesday's winning start under interim boss Lee Bullen came to a disappointing end in a 1-0 defeat to a resilient Millwall.
Connor Mahoney crossed for towering striker Smith to nod home in the 37th minute and that was all Neil Harris' side needed despite losing Jed Wallace six minutes later.
The midfielder was shown a straight red card for his challenge on Kieran Lee but MIllwall held on to bank a second win, which moves it a spot above sixth-placed Wednesday.
Charlton would have taken over in first had it beaten Barnsley.
Instead, the Addicks had to make do with a point courtesy of Lyle Taylor's late leveller from the penalty spot in a 2-2 draw at Oakwell.
Cauley Woodrow and Conor Chaplin twice gave Barnsley the lead, but Taylor held his nerve over the 89th-minute spot-kick to add to Conor Gallagher's earlier equaliser.
Stoke City and Derby County played out an entertaining 2-2 draw as Phillip Cocu avoided what would have been his first defeat in English football.
Cocu had Martyn Waghorn to thank, the striker converting a 70th-minute penalty to go with his early opener.
Liam Lindsay and Scott Hogan got on the scoresheet in between but Stoke was restricted to a point, its first of the campaign.
Derby is now eighth, two points adrift of third-placed West Bromwich Albion, which rallied from a goal down to win 2-1 at Luton Town after Grady Diangana netted a second-half double.
The largest winning margin of the day saw Nottingham Forest cruise to a 3-0 triumph over Birmingham City as the former grabbed its first win of the campaign, and the latter its first defeat.