Goals in the last 13 minutes by Mamadou Samassa and Renaud Cohade guided Valenciennes to their 10th win of the season in Ligue 1 as they condemned Lorient to their third successive defeat.
Samassa struck from close range in the 77th minute with Cohade sealing victory three minutes later.
While Valenciennes entered the game ahead of their visitors only on goal difference, they were unbeaten in three games, including a draw against Marseille last time out.
In contrast, Christian Gourcuff's side had not won in nine Ligue 1 matches and were playing their third game in the space of eight days, having lost the previous two to Lille and St Etienne.
It was the hosts who showed as an attacking force in the early exchanges.
Gael Danic shot slightly wide before David Ducourtioux missed by inches after he fired in a shot from the edge of the area following a poor defensive clearance.
The hosts threatened again when Foued Kadir pounced on a Lorient mistake to release Carlos Sanchez who shot at the goalkeeper.
Shortly after, the visitors had their first real shot on goal when Kevin Monnet-Pacquet's left-footed attempt was blocked by Nicolas Penneteau.
Kadir then freed Cohade whose 25-yard snap-shot skimmed the bar as the half ended goalless.
Monnet-Pacquet then shot inches wide before the hosts almost went ahead, Vincent Aboubakar's strike hitting the post.
Mathias Autret went close for Lorient but finally the deadlock was broken with 13 minutes left.
Kadir was involved again, his poorly-cleared cross finding Samassa who volleyed home from close range.
Cohade sealed victory with a low shot following a quick counter-attack.
