The Whites opened up a two-goal lead as they went in search of a first victory on home soil in two months, only for Britt Assombalonga to pull one back from the spot in the final quarter of the match.
Despite a nervy conclusion, Leeds held on to pick up the three points required to draw level with their opponents in sixth place, keeping their playoff ambitions well and truly alive.
Boro felt that they should have had a penalty in a quiet start to the match, as Gaetano Berardi wrestled Assombalonga to the ground when attempting to defend a corner.
That would prove to be as good as things got for the Smoggies in the first half, however, as an out-of-form Leeds side slowly grew into the match.
Not since the opening day of the season have the Smoggies managed fewer first-half shots on target, and it was not long before they found themselves with an even bigger goal margin to overcome.
Alioski had the simple tasking of helping the ball over the line at the back post following an inch-perfect delivery from Hernandez, 48 seconds after Boro youngster Marcus Tavernier rifled over the bar from a glorious position.
Leeds were looking lively at the other end, though, themselves hitting the post through Saiz's 25-yarder after linking up with Ronaldo Vieira, and they really should have had a third moments later as Cooper nodded wide when left completely unmarked.
Downing and Assombalonga were the next to try their luck for the visiting side, neither managing to test Lonergan, but the North-East outfit did drag themselves back into things with 14 minutes to play.
In a bizarre incident, Ayling was penalised for grabbing the boot of Daniel Ayala, having being left aggrieved after his opponent dragged him to the floor seconds beforehand.
After discussing the incident with his linesman, referee Keith Stroud pointed to the spot and Assombalonga converted following a lengthy delay to set up a tense finale in West Yorkshire.
Leeds successfully saw through eight minutes of added time, with Braithwaite's deflected attempt on the spin the closest Middlesbrough came to a leveller, meaning a losing return to Elland Road for former boss Garry Monk.