Before the encounter, Nicolas Usain’s men were three points off the relegation zone, but the hard-fought victory handed them some relief.
Five minutes before the half-time break, Senegalese forward Keny put the hosts ahead thanks to an assist from Jeremy Cordoval.
Mali’s Diarra doubled La Berri’s lead in the 66th minute before turning provider for Cote d’Ivoire defender Opera.
However, Lens launched an attempt to equalise following efforts from Cheick Doucoure and Simon Banza – yet they were unable to get the important third.
Following this result, Chateauroux climbed to 16th in the log having garnered 28 points from 25 outings.
For Lens, they remain second with 47 points – four points behind leaders Lorient.
They would be hoping to recover from this setback when they welcome Caen to Stade Bollaert-Delelis on Saturday.
Usain’s side take on promotion-chasing Grenoble Foot a day earlier.