O'Gara added Munster's only score of the opening half after a late hit by replacement Ben White resulted in a penalty just before the halftime whistle.
On the return Alan Quinlan scored the only try of the game with O'Gara adding the convert to give Munster the lead for the first time, 10-6. The lead was further extended after another O'Gara penalty after 50 minutes.
Playing conditions became extremely difficuly when fog rolled into Thomond Park within minutes, and the ball was barely visible. O'Gara managed a final three points when awarded a penalty directly in front of the posts to give Munster a 16-9 win this evening.
On a further postive note for Munster Paul O'Connell returned to action this evening coming on as a 57th minutes replacement for Donncha O'Callaghan.
Man of the match Damien Varley after the win "Cardiff are a very good team, we expected a tough encounter tonight and they were very physical up front. The win today is good going into next week but there are alot of things that need to be worked on. Having Paul back is fantastic, the reception he got tonight was great and everyone, supporters and players, were enthused by his return."
Munster: J Murphy; L Mafi, K Earls, S Tuitipou, D Hurley; R O'Gara, P Stringer; W du Preez, D Varley, T Buckley; M O'Driscoll, D O'Callaghan; A Quinlan, N Ronan, D Leamy captain. Replacements: M Sherry, D Ryan, J Hayes, P O'Connell, D Wallace, T O'Leary, P Warwick, B Murphy.
Cardiff Blues: Chris Czekaj; Richard Mustoe, Casey Laulala, Tom Shanklin, Gavin Evans; Dan Parks, Richie Rees; Xavier Rush, Sam Warburton, Mamma Molitika; Paul Tito, Michael Paterson; Taufa'ao Filse, Gareth Williams, Gethin Jenkins. Replacements: Rhys Williams, Tom Davies, Sam Hobbs, Bryn Griffiths, Ben White, Tom Slater, Ceri Sweeney, Dafydd Hewitt.