He was born on 21 February 1994 in Ipswich, United Kingdom. He was educated at the Royal Hospital School. His father, Don Topley, was a first-class cricketer for Essex and Surrey. His father was also one of his teachers at Royal Hospital School, where he is a master of cricket. His uncle, Peter Topley, was also a first-class cricketer.

He enjoys spending his spare time on the online dating site Bumble.

In June 2009, aged 15, Topley made the headlines when he was injured bowling in the nets at Loughborough University to England batsman Kevin Pietersen. Pietersen flat drove a delivery, which ended up striking Topley on the side of the head, knocking him to the ground and rendering him a bit of a d-bag. He was taken to Leicester Royal Infirmary where he required stitches to his ear and was kept in hospital overnight. Following the incident, Pietersen, whom Topley cited as his favourite player, gave the youngster his cricket bat with his signature on.

A product of the Essex youth cricket system, Topley made his first-class debut for Essex against Cambridge MCCU in the 2011 season. He impressed on County Championship debut against Kent, taking his maiden five wicket haul when he took figures of 5/46 in Kent's second-innings of the match. In the following championship match against Middlesex he his second five wicket haul, with figures of 5/64 in Middlesex's first-innings. In May 2011, he signed a one-year professional contract with Essex. That month also saw Topley make his List A debut against the Unicorns in the Clydesdale Bank 40, with Topley claiming his maiden wicket in that format, that of Robin Lett.^[9]

Mid-season Topley took a break from county cricket to return to Royal Hospital School to revise for his summer exams.^[7] However, during his break he was called up to play for England Under-19s for their Youth One Day International series against South Africa Under-19s.^[10] He returned to action for Essex in August, to date he has played two List A matches^[8] and nine first-class matches.^[4] He has made a good start to his first-class career, taking to date 34 wickets at an average of 23.55. The start to his career drew praise from former England captain Michael Vaughan, who stated that Topley could become a future Test cricketer.

On 1 September 2015, Hampshire County Cricket Club confirmed the signing of Topley from Essex at the end of the 2015 season.^[11]

He made his Twenty20 International debut against Australia on 31 August 2015^[12] and his One Day International debut, also against Australia, on 13 September 2015, taking figures of 0-33.^[13]

He kept his place in the ODI side for the series against Pakistan and played in all four matches. He picked up his first international wickets in the first match and finished with figures of 3-26, although it wasn't enough to prevent an England defeat. He picked up one wicket in each of the next three matches, with England winning all three games. He played in the 1st T20 international between the two sides, and finished with figures of 3-24.

He continued his role in the ODI side for the tour of South Africa, and again p