Sea Moon did not appear as a three-year-old until 11 June when he appeared in a handicap race over ten and a half furlongs at York Racecourse. Carrying top weight of 133 pounds he took the lead inside the final furlong and won by one and three quarter lengths from Flag Officer. After a break of two months, Sea Moon returned to York and was moved up in class to contest the Group Two Great Voltigeur Stakes, a recognised trial for the St Leger Stakes. Ridden by Richard Hughes in place of the injured Moore, Sea Moon took the lead in the final quarter mile and quickly drew clear of the field. Despite being eased near the finish he won by eight lengths from Al Kazeem. Marcus Armytage, writing in the Daily Telegraph, called the performance "a stunning display". In the St Leger at Doncaster Racecourse on 10 September, Sea Moon, ridden by Olivier Peslier, was made 2/1 favourite ahead of the 1000 Guineas winner Blue Bunting. Peslier restrained the colt in the early stages before attempting to challenge in the straight. He was unable to obtain a clear run and was blocked twice before switching to the outside inside the final furlong. Sea Moon finished strongly but was beaten into third place behind Masked Marvel and Brown Panther. His performance divided press opinions: some considered him an unlucky loser, while others claimed that he never looked likely to win. On his final start of the year, Sea Moon was sent to the United States for the Breeders' Cup Turf at Churchill Downs. Moore held the colt towards the rear of the field before challenging for the lead in the straight. He finished second of the nine runners, beaten two and a quarter lengths by St Nicholas Abbey.
2012: four-year-old season
Sea Moon began his 2012 campaign in the ListedSouthern Daily EchoTapster Stakes on firm ground at Goodwood on 26 May. Starting the 2/7 favourite and held of the sustained challenge of Dandino to win by a head. In the Group Two Hardwicke Stakes at Royal Ascot four weeks later, he was made 2/1 favourite against a field which included the Melbourne Cup winner Dunaden. Racing on soft ground for the first time since his win in the Great Voltigeur, Sea Moon took the lead two furlongs from the finish and accelerated clear of the field to win by three and a quarter lengths from Dunaden, with Red Cadeaux in third. After the win, Stoute announced that Sea Moon would return to Ascot for the King George VI and Queen Elizabeth Stakes a month later. Sea Moon started 2/1 favourite for the King George, but finished fifth of the ten runners behind Danedream. After a break of more than two months, Sea Moon returned in the Prix de l'Arc de Triomphe at Longchamp and finished eighth of the eighteen runners behind Solemia. In December, Sea Moon was sent to Hong Kong to contest the Hong Kong Vase but was withdrawn from the race after being diagnosed with a "blood abnormality".
2013–2014: Australian career
In January 2013 Sea Moon was sold to Lloyd Williams and sent to race in Australia where he was trained by Robert Hickmott. Sea Moon did not appear on the racecourse until September, when he finished unplaced in the Makybe Diva Stakes and the Underwood Stakes. On 5 October at Flemington Racecourse he started favourite for the Bart Cummings Stakes over 2500 metres but was beaten a nose by Araldo. A week later he won his first race for his new owners when he won the Grade Two Herbert Power Stakes over 2400m at Caulfield Racecourse. He was regarded as a leading contender for the Melbourne Cup and started 10/1 third favourite but finished unplaced behind Fiorente. He finished no better than fifth in his subsequent Australian races and in 2015 he returned to Europe to be trained in Ireland by John Oxx. Oxx reported that the horse became very ill on the voyage but recovered well and entered training in April.