Steve Bruce's side, who saw a run of seven consecutive wins ended by Fulham at the weekend, dropped more points against fellow promotion hopefuls as Preston extend their recent run to just one defeat in their last 17 matches.
The visitors took the lead through Tom Barkhuizen shortly before half time, but Lewis Grabban's penalty midway through the second half - his first goal for the club - earned Villa a share of the spoils.
The result leaves them one point adrift of second-placed Cardiff City, who are not in action until tomorrow, when they face Ipswich Town.
At the other end of the table, Burton Albion climbed off the bottom with a vital 2-1 victory away to fellow strugglers Barnsley, leapfrogging their opponents in the table and moving up to 22nd, now only in the bottom three on goal difference.
The hosts threatened a comeback when Dani Pinillos halved the deficit with 15 minutes remaining, but they could not find an equalising goal as new boss Jose Morais's first game in charge ended in a costly defeat, leaving Barnsley still winless at home since November 4.
Burton were replaced at the bottom of the table by Sunderland, who fell to defeat in their own relegation six-pointer as Zach Clough's first-half goal proved decisive for Bolton Wanderers at the Macron Stadium.
The Trotters, who are now unbeaten in six home games, climb up to 19th and four points clear of the bottom three as a result of the victory, whereas Sunderland have now taken just one point from the last 15 on offer to sink to the bottom of the pile.
The Tigers, who have still never won at the Riverside, were looking to follow up a rare victory at the weekend but succumbed to a Rudy Gestede brace either side of a Patrick Bamford strike as Boro ran out comfortable winners.
Evandro did pull Hull level at one stage, but Boro quickly restored their lead and went on to pick up a win which takes them to within two points of the playoff places.
Sheffield United remain ahead of Boro, though, having closed the gap on the top six to just one point courtesy of a 2-1 victory over Queens Park Rangers, whose woeful record on the road stretches to just two wins from their last 24 Championship away games.
Goals either side of half time from Richard Stearman and John Lundstram put the Blades en route to back-to-back home wins for the first time since November, and they held on after Luke Freeman had halved the deficit.
Goals from Ollie Watkins (2), Florian Jozefzoon, Neal Maupay and an own goal from Marc Roberts saw the Bees record only their second-ever league double over Birmingham - and their first since 1951-52 - to make it only one defeat in their last 16 Championship home games.
Birmingham, meanwhile, are now just one point above the relegation zone following a third consecutive defeat.
Reading are only four points clear of danger themselves following a 1-1 draw against Nottingham Forest at the City Ground, with Lee Tomlin rescuing a point for the home side just five minutes from time.
Omar Richards had given Reading the lead 10 minutes before half time, but the Royals could not hold on as Forest hit back with a rare goal - just the third they have scored in their last 10 Championship matches.
There were 13 minutes of added time at The Den as Millwall were made to wait for their 2-1 victory over Sheffield Wednesday, coming from behind to prevent Owls boss Jos Luhukay from following up his first league win as manager with a second in succession.
Lee Gregory and Steve Morison's second-half goals cancelled out Joey Pelupessy's opener as Millwall recorded back-to-back Championship wins for the first time since August 2014, extending their unbeaten home run to nine matches in the process.
CHAMPIONSHIP RESULTS Aston Villa 1-1 Preston; Barnsley 1-2 Burton Albion; Brentford 5-0 Birmingham; Middlesbrough 3-1 Hull; Millwall 2-1 Sheffield Wednesday; Nottingham Forest 1-1 Reading; Sheffield United 2-1 Queens Park Rangers; Bolton 1-0 Sunderland