Right wing Joe Ajuwa scored two of the Welsh tries but coach Lyn Jones was disappointed they did not gain a more emphatic win.
The back-to-back December defeats by Grenoble put an end to any hopes London Welsh had of making a real impact in their debut season in Europe.
But Jones is confident the experiences of playing against top teams like Stade Francais Paris - who gave them a torrid introduction back in October - and Grenoble will play vital roles in the development of the Premiership's newest club.
- In the reverse fixture earlier this term, London Welsh edged a thriller 32-31 to secure their first ever European victory.
- Since defeating Connacht Rugby on their European debut in October 2010, Cavalieri have lost 15 consecutive matches in this tournament, conceding an average of 48 points per game.
- Gavin Henson has kicked five goals from five attempts this season, one of only three men to have attempted five or more and retain a perfect success rate.
- Only Wasps' James Haskell has made more tackles (47) than Prato's Luca Petillo, who has completed 45.