Toulouse set up Champions Cup final against Leinster
Toulouse raced into a 31-12 half-time lead before Quins closed to five points with two tries at the start of the second half before a yellow card for Jack Walker halted the momentum for the Londoners.
"It was a hell of a match," said the home team's English flanker Jack Willis told TNT. "Fair play to Quins. But I can't wait for that match in a few weeks. It's a pretty cool feeling."
Toulouse have won the competition a record five times while Leinster are the second most successful club with four titles.
The final will take place at Tottenham Hotspur Stadium on May 25.
"A hell of a task against Leinster," said Willis. "A lot of work to go."
Leinster also held off a plucky fightback from English visitors as they beat Northampton 20-17 in Dublin on Saturday.
"The final will be unbelievable," Quins scrum half Danny Care told ITV. "We would love to have been a part of it but unfortunately not but we can be really proud of our efforts."
Both Toulouse and Leinster have appeared in seven finals, but have never met in the cup decider.
Leinster will be seeking to avoid a painful French hat-trick. They lost narrowly to La Rochelle in the last two finals.
But the Irish province have won the last three meetings with Toulouse, the two most recent were emphatic semi-finals victories in 2019 and 2022.
From the kick-off at a packed Ernest-Wallon stadium, Toulouse pinned back Harlequins.
After their powerful forwards sucked in the visiting defence, fly-half Romain Ntamack flung the ball wide to Matthis Lebel who trotted over in the corner.
Quins hit back and Marcus Smith sidestepped over for a try.
Toulouse retook the lead when hooker Peato Mauvaka squirmed over.
Quins again replied, their pack mauling the home forwards rapidly backwards, to the noisy disapproval of the home crowd, before flanker Will Evans touched down.
The tide turned to Toulouse when lock Thibaud Flament plucked the ball from the hands of flanker Chandler Cunningham-South close to Quins line and jogged over to score.
Antoine Dupont finished two rapid counter-attacks with a pair of touchdowns -- from the second Blair Kinghorn landed his third conversion and Toulouse were ahead 31-12 at the break.'Little bit shaky'
Quins, the kings of the unlikely comeback, struck at the start of the second half as Cadan Murley dived over in the corner.
Then, following a series of line breaks, Tyrone Green scooted through a huge hole in the suddenly ragged Toulouse defence. Smith landed his fourth conversion to cut the gap to five points after 54 minutes.
With 14 minutes to play, Walker received a yellow card for catching Dupont in the head.
From the lineout, Toulouse moved the ball quickly across the field and wing Juan Cruz Mallia lunged over in the corner.
Substitute Thomas Ramos kicked the conversion to seal the victory.
"We said all week prepare for the unexpected and you are still not prepared for it with Quins," said Willis.
Before this season Harlequins had never won a knockout round game in the competition.
"It would be easy for me to say we had a great run at it and we made it to the semi-finals," said Quins No. 8 Alex Dombrandt.
"But I stand here with a missed opportunity that we could have been in the final."