Ceri Sweeney should have kicked the Blues into the lead when offered an easy opportunity in the opening minutes and that miss looked all the more glaring when Keatley knocked one over from a metre inside the Blues half in the fourth minute.
Sweeney missed another opportunity in the tenth minute but he found a good position on the Munster 22 with a 12th minute penalty and when Blues went wide it needed a last gasp Denis Hurley tackle to deny Alex Cuthbert in the corner.
Referee David Wlkinson referred that one 'upstairs' and moments later he needed to go there again to determine if Xavier Rush had made the line. He hadn't and Munster's tryline remained unbreached after 255 minutes of RaboDirect PRO12 rugby.
Sweeney finally found the range form 23 metres after Munster were penalised at scrum-time but in the 21st minute when Munster walked the Blues pack backwards Keatley nonchalantly stroked over the penalty from wide on the right to out his side back into the lead.
He was on the mark again in the 32nd minute with a marvellous effort from wide on the left near half way and reprised that four minutes later to leave Munster leading 12-3 at the break.
Munster: J Murphy; D Howlett, D Barnes, L Mafi, D Hurley; I Keatley, D Williams; W du Preez, M Sherry, S Archer; B Holland, M O'Driscoll; P O'Mahony capt, T O'Donnell, J Coughlan (Ronan 28th min). Replacements: D Fogarty, J Ryan, J Hayes, D Foley, P Stringer, S Deasy, T Gleeson.
Cardiff Blues: D Fish; A Cuthbert, G Evans, D Hewitt, R Mustoe; C Sweeney, R Rees; S Hobbs, R Thomas, S Andrews, D Jones, P Tito capt, M Paterson, A Pretorious, M Molitika. Replacements: R Williams, N Trevett, R Harford, X Rush, T Young, L Jones, R Patchell, C Laulala.