The former Connacht man, who was sin-binned late on, kicked six penalties out of six as the Irish province ground out a fourth straight win at the start of the new campaign, despite barely making a visit into the Blues 22.
The hosts scored the only try through wing Alex Cuthbert with Ceri Sweeney, whose failure to kick two presentable three-point chances early on proved costly, adding the conversion and two penalties.
The Blues thought they had secured at least a draw with the last play as Cuthbert went flying in at the corner, but full-back Dan Fish's pass was forward.
Sweeney missed the chance to give the hosts an early lead as he pulled a straightforward penalty in front of the posts after James Coughlan was penalised for holding on as he attempted to counter from deep.
And Keatley showed him out it should be done by slotting a monster effort from halfway with plenty to spare.
Sweeney was again off target in the 10th minute before the Blues were twice denied the game's first try in a matter of moments.
Video referee Gareth Simmonds first adjudged that the mountainous Cuthbert put a foot in touch following a desperate tackle by Denis Hurley, and then decided that prop Sam Hobbs had been stopped short of the line.
The hosts' pressure did finally yield points after 19 minutes as tighthead Scott Andrews won a scrum penalty which Sweeney knocked over to tie the scores.
But Keatley quickly replied to re-establish the Munster lead after they dished out some set-piece medicine of their own, and he then extended the lead when the dose was repeated seven minutes before the break.
The former Connacht stand-off's deadly form with the boot continued as another long-range penalty put the Irish province out to a 12-3 interval lead.
Having lacked a cutting edge in the opening half Cardiff finally found a way of breaching the red wall as a simple pop pass from lock Paul Tito sent Cuthbert racing through 40 yards out, with the Wales Sevens man showing good pace to round Duncan Williams to cross. Sweeney added the testing conversion from out wide.
That was the first try Munster had conceded in this competition since last season's semi-final win over the Ospreys, but they quickly responded with Keatley's fifth penalty.
There were further signs of life from the Blues with a smart break from replacement Casey Laulala, but their lack of discipline was proving costly as they gave Keatley another sight of the posts just before the hour, which the fly-half gratefully took to make it 18-10.
Cuthbert continued to busy himself looking for work, and he was hauled down just short after a half-break from Sweeney.
Desperate Munster defenders infringed to disrupt quick ball and the fly-half kicked the simple penalty to bring the Blues back within five points.
Cardiff battered away at the Munster line in the dying moments, with Keatley being sin-binned as the pressure told.
And the Blues thought they had secured at least a share of the spoils in a dramatic finish but Fish's scoring pass to Cuthbert was forward.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.