Monterosso began his racing career by finishing unplaced in a maiden race on the Polytrack surface at Wolverhampton Racecourse in November 2009. In the winter he was campaigned on the all-weather track at Lingfield, finishing second in a maiden on 15 January and then recording his first win in a similar event eight days later. On 6 February he carried top weight of 133 pounds and won a one mile handicap race at the same venue. Monterosso contested his first turf race in April when he won the Cock of the North Handicap at Ripon by a neck from the fillyEleanora Duse, a subsequent Group Two winner. After finishing second to Green Moon in the London Gold Cup he was a comfortable winner of a handicap at Newmarket under top weight of 130 pounds. His performances since the start of the year had seen his official rating improve from 78 to 104, and he was thereafter campaigned in Group Races. At Royal Ascot, Monterosso contested the Group Two King Edward VII Stakes over one and a half miles. Ridden by Frankie Dettori, he took the lead early in the straight and "quickened clear" to win by two and a quarter lengths from the subsequent St Leger winner Arctic Cosmos, with The Derby runner-up At First Sight in fourth place. Monterosso's continuing improvement resulted in his owners paying €150,000 to supplement the horse into the Irish Derby at the Curragh on 27 June. He started 3/1 favourite for the race, but was never able to reach the lead and finished fourth to Cape Blanco. Monterosso was again made favourite in the Deutsches Derby three weeks later, but finished seventh behind Buzzword. He returned to England for the Great Voltigeur Stakes at York in August but was "never a factor" and finished fifth of the ten runners behind Rewilding. At the end of the 2010 season, Monterosso's ownership was transferred to the Maktoum family's Godolphin Racing operation and he was sent to Dubai to be trained by Mahmoud Al Zarooni. Another of Johnston's best three-year-olds, a chestnut named Capponi, also made the move.
2011: four-year-old season
On his first start for his new trainer, Monterosso contested the Group Two Dubai City of Gold over twelve and a half furlongs on turf at Meydan Racecourse. Ridden for the first time by Mickael Barzalona he took the lead in the straight and won by one and a quarter lengths from his stable companion Calvados Blues. Monterosso was then brought back in distance to ten furlongs and switched to tapeta for the world's most valuable race, the Dubai World Cup. Starting as a 40/1 outsider he tracked the leaders and stayed on well in the closing stages to finish third, beaten half a length and a neck by the Japanese runners Victoire Pisa and Transcend. Monterosso missed the rest of the 2011 season after contracting colic.
2012: five-year-old season
After a break of more than eleven months, Monterosso returned to the racecourse for the third round of the Al Maktoum Challenge at Meydan on 10 March. He finished fourth of the fourteen runners, six and a half lengths behind his stable companion Capponi. For his second attempt at the Dubai World Cup, Monterosso started at odds of 20/1 against twelve opponents on the evening of 31 March. Barzalona settled the horse in the middle of the field before moving strongly through to dispute the lead in the straight. He overtook Capponi one and a half furlongs from the finish and drew clear to win "comfortably" by three lengths. As he had done when winning the Epsom Derby on Pour Moi, Barzalona celebrated before the finish by standing up in his stirrups and waving his whip to the crowd. After the race the Godolphin spokesman Simon Crisford announced that Monterosso and Capponi would return to England for the rest of the European flat season, although a run in the Singapore Airlines International Cup was also being considered. Monterosso made his next appearance in the Eclipse Stakes at Sandown on 7 July. He tracked the leaders and briefly reached third place in the straight but faded in the closing stages to finish eighth of the nine runners behind Nathaniel.
2013: six-year-old season
Monterosso returned to Dubai in the winter of 2012/2013 but made only one appearance in the 2013 season. On 9 March he finished tenth of the twelve runners in the third round of the Al Maktoum Challenge.
