Pat Richards scored the only points of the first half, crossing after two minutes but missing the conversion.
Rhys Hanbury missed a penalty to leave Catalans 4-0 ahead at the break, before Vincent Duport widened the gap.
Corey Thompson and Hanbury drew Widnes level, but tries from Dave Taylor and Eloi Pelissier and a Thomas Bosc drop-goal sank Widnes late on.
Super League's surprise package Widnes suffered a disastrous Easter weekend, losing 28-10 to league leaders Warrington on Easter Friday before going down 20-12 to St Helens on Monday.
And they travelled to France to take on a Catalans side who had secured convincing wins over Salford Red Devils and Castleford Tigers during the same period.
Having trailed by four points at half-time, the Vikings produced a spirited display and battled back to 8-8 courtesy of a lovely floated pass from Joe Mellor out to Thompson and Hanbury's penalty following a Catalans' high tackle.
But Taylor pounced on a loose ball as Catalans scored a fortuitous try before Bosc slotted a drop-goal and Eloi Pelissier stretched for the line to leave the French outfit level on points with third-placed Widnes in the table.
Catalans: Escare, Broughton, Gigot, Duport, Richards, Bosc, Myler, Bousquet, Pelissier, Mason, Stewart, Taylor, Baitieri.
Replacements: Aiton, Mounis, Elima, Maria.
Widnes: Hanbury, Thompson, Dean, Runciman, Ah Van, Mellor, Gilmore, O'Carroll, Heremaia, Dudson, Whitley, Houston, Leuluai.
Replacements: Manuokafoa, Chamberlain, Brooks, Johnstone.
Catalans recorded their third win in nine days as early pacesetters Widnes fell to a third successive defeat.