An opportunistic first-half score from Ruan Pienaar put Ulster on course for their second win in three matches.
Andrew Trimble looked to have wrapped it up after 45 minutes, before Gael Fickou led a Toulouse fight-back, but Luke Marshall’s late score sealed their third win on French soil.
Ulster captain Rory Best believes their European Champions Cup double over Toulouse has proven their doubters wrong.
Question marks over the Irish side’s credentials emerged when Saracens romped to a 27-9 triumph at the Kingspan Stadium in round two.
Ulster recovered to score back-to-back triumphs over European rugby’s most successful side.
Luke Marshall latched on to an inside ball to go over the try-line five minutes from time and secure Ulster’s third win on French soil.
There was still time for Louis Picamoles to set up a tense finish with a drive-over try — but Best’s men held-on to get back in the quarter-final race.
The Ulster skipper always believed things would turn around after a disjointed start to the season.
He said: “We had a lot of doubters after the Saracens game but we knew we were doing a lot of good things.
“We were very rusty against Saracens when boys were coming back from the Rugby World Cup with our new coach coming in.
“Wholesale changes haven’t been made, but we are making little tweaks and they are starting to bear fruit.
“We knew it was going to be a very tough place to come and win — and that proved to be the case.
“But the way the boys fought back against their momentum with our defence and our willingness to get back into the line was great, I can’t ask for more as a captain.
“We’re not the biggest team, we don’t have players who weigh 130 kilos, but what we do have is a lot of heart, a lot of fitness, and a very good skill level in the forwards with some exciting backs.
“The best thing for us is to utilise that by playing at a high tempo, and when we get front-foot ball, Ruan Pienaar and Paddy Jackson can really pull the strings.”
Tries: Fickou, Picamoles. Cons: Bezy, Doussain. Pens: Bezy 3.
Palisson, Kunatani, Fickou, Fritz, Matanavou, Doussain, Bezy, Baille, Marchand, Johnston, Lamboley, Maestri, Camara, Dusautoir, Harinordoquy.
Poitrenaud for Matanavou (60), Mele for Bezy (76), Steenkamp for Baille (52), Tolofua for Marchand (52), Muller for Johnston (37), Picamoles for Dusautoir (59), Tekori for Harinordoquy (52).
Tries: Pienaar, Trimble, L. Marshall. Cons: Jackson 2. Pens: Jackson 2.
Ludik, Trimble, L. Marshall, McCloskey, Gilroy, Jackson, Pienaar, McCall, R. Best, Herbst, O’Connor, van der Merwe, Diack, Reidy, Wilson.
Scholes for Gilroy (12), P. Marshall for Pienaar (77), Warwick for McCall (52), Lutton for Herbst (44), Stevenson for O’Connor (76), Williams for Reidy (43), Herring for Wilson (62).
JP Doyle (RFU).