Harlequins director of rugby Conor O'Shea has said that Sunday's felt like winning the Heineken Cup final itself.
The win leaves the London side within a point of group leaders Toulouse in the fight for a quarter-final place.
Nick Evans kicked 16 points, while Mike Brown scored two tries and Joe Gray one in the London side's win.
"It feels like we've won a cup final but it's a pool game," said O'Shea. "We have to make sure we keep learning."
The win reverses Quins' at home to Toulouse a week earlier and is the first win by an English team in the French city since Saracens' 32-22 win 11 years ago.
The defeat was the first at home in European competition for nearly three years for Toulouse, who have won the Heineken Cup four times in its 15-year history.
"We have shown how quickly we can learn at this level," said O'Shea. "We were disappointed with a few things from the previous game at the Stoop but we got our line-speed in defence right and that pressured them into mistakes.
"The resolve the players showed was incredible," added O'Shea.
"We have a good record away from home but we knew coming here we were going to have to ride our luck at times in the face of wave after wave of pressure.
With a quarter-final place on the line in the two remaining games against Gloucester and Connacht, O'Shea is warning his players against complacency.
"We won't stick our heads in the sand and say it was a perfect performance," he said. "But these are the days that make the Heineken Cup and the games you are judged on."