Harlequins outscored London Irish three tries to none to win 23-9 in Saturday's Premiership clash at Twickenham Stoop.
Quins had to wait until the dying stages to kill off the Exiles but two late tries eventually secured victory.
Conor O'Shea's charges went into the match knowing that a win was an absolute necessity if they had any hope of making the play-offs, with a nine-point gap having opened up between themselves and fourth place, and they made a perfect start.
Former All Black fly-half Nick Evans gave them a seven-point lead with a little over 10 minutes gone as he collected his own chip over the top of the defence to score under the posts and added the conversion with ease.
Evans added a penalty later in the first half as well but the visitors had their moments and James O'Connor made sure they were rewarded for their possession and territory by kicking three penalties of his own to leave the score finely balanced at 10-9 at the break.
Marland Yarde, who will be making the move to the Stoop at the end of the season, made things difficult for the Exiles in the early stages of the second half by picking up a yellow card but it was testament to their defence that the only points that they conceded during the 10 minutes down to 14 men was the resultant Evans penalty.
And Irish were still very much in with a chance of picking up another away victory, after they had won three of their previous five matches on the road, going into the final 10 minutes.
Quins did seal the win that they so desperately needed though with two late tries.
Winger Sam Smith finished off the first of them after an excellent driving maul had created the overlap and the Six Nations player of the tournament Mike Brown marked his return to the side by putting the icing on the cake.
He came into the line to score in the corner after some concerted Harlequins pressure and, although there wasn't enough time left for the hosts to grab the all-important bonus point try, they will be satisfied to be back to winning ways after losing two of their previous three games.
Tries: Evans, Smith, Brown
Pens: Evans 2
For London Irish:
Yellow card: Yarde
Harlequins: 15 Mike Brown, 14 Ollie Lindsay-Hague, 13 Matt Hopper, 12 Jordan Turner-Hall, 11 Sam Smith, 10 Nick Evans, 9 Danny Care, 8 Nick Easter, 7 Chris Robshaw (c), 6 Luke Wallace, 5 George Robson, 4 Nick Kennedy, 3 Kyle Sinckler, 2 Dave Ward, 1 Joe Marler
Replacements: 16 Max Crumpton, 17 Mark Lambert, 18 Paul Doran Jones, 19 Charlie Matthews, 20 Tom Guest, 21 Karl Dickson, 22 Ben Botica, 23 Tim Molenaar
London Irish: 15 James O'Connor, 14 Topsy Ojo, 13 Fergus Mulchrone, 12 Eamonn Sheridan, 11 Marland Yarde, 10 Shane Geraghty, 9 Tomás O'Leary, 8 Ofisa Treviranus, 7 Blair Cowan, 6 Kieran Low, 5 Nic Rouse, 4 George Skivington (c), 3 Jamie Hagan, 2 Jimmy Stevens, 1 Matt Parr
Replacements: 16 Mike Mayhew, 17 John Yapp, 18 Leo Halavatau, 19 Jebb Sinclair, 20 Gerard Ellis, 21 Alex Lewington, 22 Myles Dorrian, 23 Darren Allinson
Venue: Twickenham Stoop
Referee: Andrew Small
Assistant referees: Gareth Copsey, Andy Watson
Television match official: Keith LewisLewis