Bella Estrella held off Hence to land the Listed Irish Stallion Farms EBF Cairn Rouge Stakes at Killarney.
Winner of her first two starts last year, on her only outing this season the four-year-old finished fourth of six at Gowran.
As a result the High Chaparral filly was sent off at 12-1 under Declan McDonogh, but showed a really willing attitude in the closing stages.
Having hit the front a furlong out, she began to look vulnerable as Aidan O'Brien's Hence surged out of the pack, but stuck her neck out for a valuable black-type success.
The well-fancied Petticoat lost all chance when slowly out of the stalls.
"I have to congratulate the staff for the ground conditions, as it is a credit to them - they never get it wrong here and that's what helped her today as she needed that bit of cushion underfoot," said McDonogh.
"The boss said she'd put up a good fight and was confident she'd run a big race, she truly did that and is a valuable filly now.
"She was game when the second-placed filly came to her and she was never getting by. The Listed race in Galway might be a target, I'm not sure, but it was great to get today over with."
Elsewhere on the card, Aidan O'Brien's Anthony Van Dyck took a giant leap forward from his debut to run out a wide-margin winner of the Irish Stallion Farms EBF Maiden.
A son of the great Galileo, he finished seventh of 10 on his debut at the Curragh, but was sent off the 10-11 favourite to oblige on this occasion.
While he had to be rousted along a couple of furlongs out by Donnacha O'Brien, once he hit top gear the race was over.
He careered clear inside the final furlong to beat Yonkers by eight lengths.
Anthony Van Dyck finished the race off so strongly O'Brien struggled to steer him around the bend after the line and he collided with some plastic railing, but there was no harm done.
The rider said: "He did it really nicely today.
"They went a good gallop out in front and around here it's not easy to make up ground, so I just wanted to get him rolling early. Once I got a few slaps into him he really picked up.
"He'd give you a similar feel to Kew Gardens (a winner at Killarney last year) and I think he's a smart horse.
"There are sharp bends here and there were a few people around in high-vis jackets and with two-year-olds like that, they don't concentrate and he went through the rails before he knew what he was doing.
"It was just greenness."