[3] Horsfield was selected for the 2015 Walker Cup at Royal Lytham & St Annes Golf Club but withdrew two weeks before the event.

[7] He had a useful start to 2018, with a 4th place in the ISPS Handa World Super 6 Perth and finishing second at the Tshwane Open, two strokes behind George Coetzee.

In early August 2020, Horsfield had his breakthrough win on the European Tour when he won the Hero Open by one shot over Thomas Detry.

[9] Two weeks later, Horsfield won his second European Tour event at the Celtic Classic in Wales, two strokes ahead of Detry, who finished as runner-up again.

[11][12] Horsfield was part of the inaugural LIV Golf event at Centurion Club at London, where he placed 5th, winning $975,000.