Hartley began his cricket journey playing for local clubs before breaking into the professional scene with Lancashire. He has been a key player for Lancashire in domestic competitions, particularly in the Vitality T20 Blast and the Royal London One-Day Cup. Hartley is known for his economical bowling, ability to take wickets in crucial moments, and his composure under pressure. His performances in T20 cricket, especially for Lancashire and Manchester Originals in The Hundred, have caught the attention of selectors and cricket fans alike, marking him as a player to watch for the future.