Cliffs of Moher made his racecourse debut in a seven furlongmaiden race at Cork Racecourse on 15 October in which he was ridden by his trainer's son Donnacha O'Brien. Starting at odds of 4/1 in a fourteen-runner field he kept on well in the closing stages without ever looking likely to win and came home fifth, more than nine lengths behind the winner Spanish Tenor. Two weeks later in a similar event at Leopardstown Racecourse the colt was ridden by Seamie Heffernan and started 7/2 third choice in the betting behind his stablemate Orderofthegarter. Despite sweating up before the race he went to the front soon after the start and was never headed thereafter, winning "easily" by five and a half lengths from Orderofthegarter.
2017: three-year-old season
On his first appearance as a three-year-old, Cliffs of Moher was sent to England to contest the Dee Stakes over ten and a half furlongs at Chester Racecourse on 12 May. He was ridden by Ryan Moore and started the 4/5 favourite against seven opponents headed by the Michael Stoute-trained Mirage Dancer. He was amongst the leaders from the start, took the lead a furlong out and won by one and a half lengths from the Godolphin representative Bay of Poets. On 3 June Cliffs of Moher was one of six Ballydoyle runners in an eighteen-runner field for the 238th running of the Epsom Derby and started the 5/1 second favourite after being selected by the stable's top jockey Ryan Moore. After being restrained towards the rear of the field, he made rapid progress on the outside in the straight. He overtook the favourite Cracksman inside the last furlong, but was caught in the final strides by the outsider Wings of Eagles and beaten three-quarters of a length into second place. The colt was then dropped in distance and matched against older horses in the Eclipse Stakes over ten furlongs at Sandown Park on 8 July. He was made the 7/4 favourite, but lost his chance after being badly hampered and finished fourth behind Ulysses who won by a nose from Barney Roy. At York Racecourse in August the colt started at odds of 9/2 in the International Stakes. In a change of tactics he led from the start but was overtaken in the straight and finished fourth behind Ulysses, Churchill and Barney Roy.
2018: four-year-old season
Cliffs of Moher was renamed The Cliffsofmoher when sent to race in Australia in October 2018, to avoid confusion with another horse already running in Australia. The Cliffsofmoher broke down during the 2018 Melbourne Cup, reportedly breaking his right shoulder, and was subsequently put down.