A last-minute score from Denis Hurley saw Munster break Scarlets' hearts in 22-20 victory at Parc y Scarlets on Saturday.
Trailing 20-15 and with only a couple of minutes left on the clock, the flying wing burst through some desperate defence to collect his second try and Munster's second win of the campaign.
Up until then the Scarlets had looked like repeating their opening-day win over fellow Irish province Leinster, but will rue a string of missed kicks at goal.
Munster too had an off-day with the boot, but in the end Hurley's brace proved crucial.
With both sides still resting their British & Irish Lions contingent, it was the Scarlets who were quickest out of the blocks, although fly-half Rhys Priestland missed two penalties to give his side the advantage their early pressure deserved.
Munster then had Ireland number eight Denis Leamy sin-binned for an offence at a ruck and, after another infringement by the visitors, the young home fly-half finally found his range from close in front.
The lead did not last long, however.
The champions responded with a penalty from fly-half Jeremy Manning and should have crossed for the game's first try, but centre Lifeimi Mafi spilled a pass with the line at his mercy.
The Irish province were celebrating on 25 minutes when Hurley dived over in the corner after a fine pass from scrum-half Toby Morland, with Manning converting superbly from the touchline.
Ill-discipline was costing the visitors dear and Munster received their second yellow when lock Donnacha Ryan was dispatched for taking Scarlets full-back Daniel Evans out in mid-air. Replays suggested the decision was harsh.
The Scarlets were not complaining though and levelled matters with a superb breakaway score five minutes from half-time.
Scotland wing Sean Lamont began the movement from his own 22 and after good support work from centre Jonathan Davies and flanker Simon Easterby it was prop Deacon Manu of all people who popped up to take the try-scoring pass, diving over unopposed at the posts. Priestland landed the simple conversion.
It got better for the Scarlets five minutes after the restart. A midfield surge from full-back Evans had the Munster defence scampering back onto their own line and, after strong work by the forwards, skipper Mark Jones was driven over close to the posts.
Priestland's conversion made it 17-10, but back came Munster with an opportunist try from former Waikato Chiefs scrum-half Toby Morland after Scarlets number nine Martin Roberts had been robbed on his own line.
It was nervy stuff with Priestland failing to ease his side's nerves by missing another strike on goal, before watching opposite number Manning push a long-range effort just wide.
After taking over the kicking duties from Priestland, Daniel Evans made it 20-15 three minutes before the end.
But two minutes into stoppage time Hurley burst through the defence from 30 metres out and Manning kept his nerve to nail the conversion to seal the four points.
Tries: Manu, M Jones
Con: Priestland 2
Pen: Priestland, Evans
Tries: Hurley 2, Morland
Con: Manning 2
Scarlets: 15 Daniel Evans, 14 Sean Lamont, 13 Gareth Maule, 12 Jonathan Davies, 11 Mark Jones (capt), 10 Rhys Priestland, 9 Martin Roberts, 8 David Lyons, 7 Dafydd Jones, 6 Simon Easterby, 5 Dominic Day, 4 Lou Reed, 3 Rhys Thomas, 2 Ken Owens, 1 Iestyn Thomas.
Replacements: 16 Phil John, 17 Emyr Phillips, 18 Deacon Manu, 19 Vernon Cooper, 20 Richie Pugh, 21 Lee Williams, 22 Dan Newton.
Munster: 15 Felix Jones, 14 Doug Howlett, 13 Barry Murphy, 12 Lifeimi Mafi, 11 Denis Hurley, 10 Jeremy Manning, 9 Toby Morland, 8 Denis Leamy, 7 Niall Ronan, 6 Alan Quinlan, 5 Mick O'Driscoll (capt), 4 Donncha Ryan, 3 John Hayes, 2 Damien Varley, 1 Julien Brugnaut.
Replacements: 16 Denis Fogarty, 17 Tony Buckley, 18 Billy Holland, 19 Tom O'Donnell, 20 Tomas O'Leary, 21 Scott Deasy, 22 Tom Gleeson.
Referee: Alain Rolland (Ireland)
Assistant referees: Nigel Whitehouse (WRU), Martyn Lewis (WRU)
TMO: Huw Lewis (WRU)