It was a typical Liverpool mixture of smash-and-grab attacking and stout defending, but another example of why the Merseysiders cannot be ignored as the race reaches its climax.
Nicolas Anelka was an impressive Liverpool spearhead and created a first half opener for Emile Heskey.
John Arne Riise added the second to confirm the win as Liverpool threw down the gauntlet to the title-chasing pack of Manchester United, Arsenal and Newcastle.
And despite a brave rally from Steve McClaren's side that brought a late goal for Gareth Southgate, Liverpool remained rock steady to record a fifth successive away win.
Middlesbrough were left to harbour renewed relegation worries, but showed tremendous spirit as they threatened to spring a shock for long periods.
Liverpool were still unable to recall hamstring injury victim Michael Owen, while Steven Gerrard was rested with the Champions League decide with AS Roma in mind.
But they were not missed as Liverpool's all-round resilience and squad strength saw them through another testing encounter.
Middlesbrough were dealt a blow prior to kick off when striker Noel Whelan was ruled out with a throat infection, but Benito Carbone returned after being cup tied.
McClaren's men were high on adrenalin and condidence after reaching the FA Cup semi-final and staging a recent league recovery - and it showed as they dominated the opening half-hour.
Liverpool were on the back foot as early as the second minute when Jerzy Dudek saved well from Frank Queudrue's header, and they stayed there for much of the half.
But Liverpool, with the rejuvenated Anelka a constant source of danger, were always in the hunt and the France striker brought a fine save out of Mark Schwarzer in a rare counter attack.
Paul Ince shot narrowly wide against his former club and Stephane Henchoz was booked for a clumsy challenge on Carbone as MIddlesbrough pressed.
But Middlesbrough were almost undone by a moment of carelessness after 29 minutes when a mix-up between Schwarzer and Gianluca Festa forced the goalkeeper into a desperate retreating save from Heskey.
It was a brief reprieve as Liverpool went ahead three minutes later when England marksman Heskey was on target.
Anelka, inevitably, was the creator with a brilliant left-flank run, and when Schwarzer only parried Doetmar Hamann's shot, Heskey scored from six yards.
Queudrue was proving a danger at set pieces, and Liverpool were grateful for Vladimir Smicer's goal-line clearance from a header after 54 minutes.
Liverpool were not simply content to sit back as they chased a vital three points, and Sami Hyypia was brilliant denied by Schwarzer as he powered Danny Murphy's corner towards goal.
Ince was driving Middlesbrough forward as they went in search of the point that could prove crucial in their battle against relegation, and he was narrowly off target after 81 minutes.
It was Middlesbrough's final fling as Liverpool doubled their advantage a minute later with a typically emphaitc finish from Riise.
Heskey's flick caught Middlesbrough short of numbers at the back, and the Norwegian thumped a brilliant strike past Schwarzer from an angle.
Southgate pulled a goal back with a header in the dying seconds, but it was Liverpool who were celebrating again at the final whistle.