St Etienne took top spot in Ligue 1, at least overnight, as Benjamin Corgnet scored twice to set up victory at the Stade du Hainaut.
Corgnet gave the visitors a half-time lead and struck again after Romain Hamouma had doubled the lead.
Maor Melikson pulled a goal back with a penalty but ASSE lead the standings at least until Monaco take on Lorient on Sunday lunchtime.
Corgnet was the provider for Les Verts' first chance five minutes in but Hamouma's low drive was saved by Nicolas Penneteau.
However the goalkeeper was culpable for the opening goal, diverting Faouzi Ghoulam's cross straight to Corgnet who finished calmly with Penneteau still on the ground.
Hamouma almost added a freak second goal before the half-hour as the ball broke goalwards out of a tackle, but Lindsay Rose cleared off the line to keep Valenciennes in touch at half-time.
But three minutes into the second period, it was 2-0 as Jeremy Clement teed up Hamouma to fire home from 25 yards with Penneteau helpless.
Corgnet and Hamouma continued to link up, forcing Penneteau to beat away a shot from the latter in the 53rd minute.
The pair were not to be denied, though, and another combination a minute later ended with Corgnet finishing first time through the legs of the beleaguered Penneteau.
It was almost 4-0 as Mevlut Erding headed Franck Tabanou's cross against the post, but as St Etienne eased off in the final half-hour they allowed the hosts to grab a consolation goal.
Moustapha Bayal Sall handled in the penalty area and Melikson powered home the penalty despite a slight touch from goalkeeper Stephane Ruffier.