Mustashry is a bay or brown gelding with a small white star bred in England by his owner, Hamdan Al Maktoum's Shadwell Estate The colt was sent into training with Michael Stoute at the Freemason Lodge Stable in Newmarket, Suffolk.
[7] The colt then moved up to handicap races for his next three starts beginning with the Britannia Stakes at Royal Ascot in which he finished twelfth under a weight of 127 pounds.
On his final run of the season he was moved up in class and finished fourth behind Quebee in the Listed Fortune Stakes at Doncaster Racecourse on 14 September.
Eleven days later at Chelmsford Mustashry carried 136 pounds in the Moulsham Mile Handicap and produced a strong late run to win by half a length from Masham Star.
[9] In August at York the colt was stepped up to Group 3 class for the Strensall Stakes and started 5/2 favourite ahead of six opponents including Mondialiste (Arlington Million), Master The World and Sovereign Debt (Sandown Mile).
Mustashry raced just behind the leaders before overtaking the front-running Forest Ranger inside the final furlong and was "driven out" by Crowley to win by three quarters of a length.
Starting at odds of 11/4 in a five-runner field he raced in third before taking the lead approaching the final furlong and won "readily" by half a length from Spark Plug.
"[13] When he attempted to repeat his 2017 success in the Strensall Stakes at York in August he took the lead a furlong out but was overtaken in the closing stages and beaten half a length by Lord Glitters.
Mustashry went to the front a quarter of a mile from the finish and after being overtaken a furlong out he rallied to regain the advantage in the final strides and won by a neck and a short head from D'bai and Dutch Connection.
Ridden by William Buick he started a 16/1 outsider and came home eleventh behind Expert Eye, beaten four lengths by the winner after being denied a clear run in the last quarter mile.
Mustashry began his 2019 campaign when he was partnered by Dane O'Neill in the Earl of Sefton Stakes over eight and a half furlongs at Newmarket on 18 April and finished third behind Zabeel Prince and Forest Ranger.
He went off at odds of 9/1 in a fourteen-runner field which included Laurens, Without Parole, Billesdon Brook, Romanised, Accidental Agent, Lord Glitters and Beat The Bank (Celebration Mile).The Britannia Stakes winner Ostilio set the pace before giving way to Laurens two furlongs out but Mustashry, who had settled well just behind the leaders, accelerated into the lead a furlong from the finish and drew away to win by two and a half lengths.
[2] At Royal Ascot in June Mustashry started second favourite for the Group 1 Queen Anne Stakes but came home seventh behind Lord Glitters after being hampered a furlong from the finish.