Despite playing in the wind in the first-half, Leinster found themselves 13-9 up at the break as McFadden kicked eight points and Isaac Boss rumbled over for a try.
With kicking conditions woeful for Leinster in the opening 40 minutes, after a series of pick-up and drives - Boss was adjudged to have got the ball down amidst an avalanche of bodies on ten minutes.
Ceri Sweeney ensured Cardiff stayed within touching distance at the break, kicking three penalties but with eight Blues on international duty and Chris Czekaj and replacement scrum-half Lewis Jones dropping out late through injury and illness - Leinster never looked in trouble.
Despite having the best of the conditions in the first-half - Cardiff's below-par line-outs and needless handling errors and turnovers - ensured Leinster always had their noses in front.
Three minutes after the break McFadden nudged Leinster further in front with a well-taken penalty but just two minutes later the game was effectively sealed for the Irish team.
Fionn Carr was the architect of the score, breaking from deep and Nathan White was in support to charge over from close range for a popular score - McFadden again added the extras.
McFadden ensured the scoreboard kept ticking over as he landed a drop goal just before the hour to extend Leinster's score to 26-9.
Despite the needless sin-binning of Leo Cullen on 54 minutes - Cardiff were unable to take advantage of their numerical advantage and just minutes later Richie Rees was also yellow carded for the visitors.
Instead it got worse for the Blues on 63 minutes as Ian Madigan scored Leinster's next try, crashing over, with the ever reliable McFadden adding the extras.
Leinster wrapped up the bonus point win as Irish international Jonathan Sexton stepped off the bench for the final quarter.
First his kick through was picked up for David Kearney to score on 68 minutes and just minutes later the duo were at it again as Sexton once again set up his team-mate for a try.
And Leinster brought up their half century in the final minutes as Leo Auva'a went over from a tap penalty after Cardiff were penalised at scrum time.
|Leinster Rugby Score Card|
|Cardiff Blues Score Card|