The hosts, who included former Leinster, Connacht and Ireland back Mark McHugh in their line-up, started strongly.
Nice scored first through a fifth minute penalty but Leinster soon gained an advantage through winger Simon Keogh who scored a try, seven minutes later, after good work from centre Isa Nacewa.
Leinster piled on the pressure with Malcolm O'Kelly putting in an excellent shift in a dominant pack and on 24 minutes Kevin McLaughlin displayed good strength to score his side's second try, which Nacewa converted, to push Leinster into a 12-3 lead.
Debutant Berne then scored a deserved try, four minutes later, to give the Irish side a 17-3 half-time lead.
Leinster continued their try-scoring ways in the second half and replacement scrum half Chris Keane touched down in the 45th minute. Nacewa again converted to push the lead to 21 points.
New Zealand triallist Billy Ngawini showed good footwork and pace to touch down on 66 minutes after some more excellent forward play, with Berne again adding the points as Leinster turned the knife in warm conditions on the south-east coast of France.
A number of the Leinster Academy players impressed, with Brendan Macken unfortunate to see a first half try disallowed.
Meanwhile, Michael Cheika's charges will continue their pre-season preparations next Friday (August 28) when they welcome London Irish to Donnybrook (kick-off 7pm). Terrace tickets are on sale here.
LEINSTER: Niall Morris; Shane Monahan, Brendan Macken, Isa Nacewa, Simon Keogh; Shaun Berne, Paul O'Donohoe; Stan Wright, John Fogarty, Mike Ross, Trevor Hogan, Malcolm O'Kelly, Stephen Keogh (capt), Shane Jennings, Kevin McLaughlin.
Replacements used: Chris Keane for O'Donohoe (32 mins), Paul Ryan for Jennings, Leo Cullen for O'Kelly, Ronan McCormack for Ross, Shane Horgan for Monahan, Billy Ngawini for Simon Keogh (all half-time), Jason Harris-Wright for Fogarty (56), David Moore for Keane, Simon Keogh for Macken, Shane Monahan for Morris (all 61), Eoin Sheriff for McLaughlin (66), Shane Jennings for Hogan (68), John Fogarty for Harris-Wright (72).