Feret put the home side ahead after just four minutes with a fine finish and he was also involved in the build-up to Rennes’ second goal in the 70th minute, which was scored by Pitroipa.
The victory was Rennes’ first in three games and saw them move to within three points of second-placed Paris St. Germain.
Valenciennes, meanwhile, remain in eighth after losing for a third time in five matches.
Rennes dominated the early exchanges and, after Romain Alessandrini had been denied by visiting goalkeeper Nicolas Penneteau, the hosts took the lead when Cheick Diarra delivered a superb pass to Feret on the edge of the box and the striker produced an equally memorable finish to find the back of the net.
The same Rennes pair combined again in the 11th minute but this time Penneteau was able to save from Diarra after he had been set up by Feret.
Valenciennes finally gave Rennes goalkeeper Benoit Costil something to do in the 19th minute when Mathieu Dossevi tried his luck, but there was no way through and it was a similar story on the half-hour when Vincent Aboubakar failed to make the most of a poor back-pass from home defender Kevin Theopile Catherine.
The visitors created another opening at the start of the second half and Jose Saez was unfortunate to see his 25-yard half-volley go just wide.
That scare seemed to spark Rennes back into life and Abdoulaye Said Dialler and Pitroipa both went close before the latter made it 2-0 with 20 minutes to go.
Feret stole possession on the halfway line and started a counter-attack that saw Pitroipa released on the right of the area and he beat
Penneteau with a low right-footed drive to seal the victory.