After a scrappy opening 10 minutes the game burst into life after a Foued Kadir strike gave Valenciennes a 13th-minute lead.
Two minutes later it was 2-0 and a dream start for the visitors; this time Carlos Sanchez finished superbly from inside the box.
Toulouse started to get back into the game and Franck Tabanou met a cross from a good position in the 34th minute but could not hit the target.
Wissam Ben Yedder then had a great chance just before half-time but his effort was well-saved and the visitors took a two-goal cushion into the break.
Then 11 minutes into the second period Ben Yedder did get on the scoresheet, heading home from an Aymen Abdennour cross.
Toulouse continued to press but Tabanou could still not find a way through as his shot after 71 minutes was blocked.
They finally managed to grab the equaliser in the last minute courtesy of an Adrien Regattin strike.