Denly played age group cricket for Kent and began his professional career with the county before moving to Middlesex for three seasons between 2012 and 2014.

He played age group cricket for England and made 14 one-day appearances for the international team between 2009 and 2010 before falling out of favour with the national selectors.

[9] Denly scored his maiden professional century in 2007, carrying his bat for 115 not out out of a Kent total of only 199 against Hampshire at Canterbury.

[10][11] In July Denly was called up to the England Lions squad for the match against India, and made 83 off 90 balls.

He did, however, make a career best score of 149 against Somerset at Tunbridge Wells and go on to end the season as one of the year's highly rated players.

[21] He signed a long-term contract extension during August 2016,[22] having made headlines earlier in the year when he retired not out in a County Championship match against Derbyshire at Derby when his wife went into labour unexpectedly early with the couple's first child.

[26][27] After signing a contract extension in August 2016,[28] Denly further improved his first-class high score on 21 May 2017 when he made 227 in the second innings of a Championship match against Worcestershire.

Denly played for England age group sides from under-17 to under-19 levels, scoring three half-centuries in consecutive matches for the under-19s in India in 2005.

[37][48][49] Following an injury to Liam Dawson, Denly was called into the England limited-overs squad during the tour of Sri Lanka,[50][51] though he did not play in the ODI series.

He scored 20 runs, opened the bowling and took four wickets on his return to the England side, winning the player of the match award.

[59][60] The following month, Denly played in his first ODI match for ten years, in the one-off fixture against Ireland in Malahide.

[63][64] and in June was selected included in England's 30-man squad to start training behind closed doors for the Test series against the West Indies.

[67] After playing for Barisal Burners in the 2012–13 Bangladesh Premier League and returning to the country in 2014 to play for Brothers Union in domestic limited overs cricket, Denly was selected in 2017 by Dhaka Dynamites as an overseas player in the Bangladesh Premier League draft.

[69][70] In 2018, Denly joined the Sydney Sixers as a replacement for Jason Roy when he was selected by the national team in the 2017-18 Big Bash League season.

In September 2018 Sydney Sixers announced that they had re-signed Denly for whole of the 2018–19 Big Bash,[31][74] although following his selection for the England tour to the Caribbean he was only able to play of the side until early January.

[80][81][82] His maiden first-class century, a score of 115 not out, was made in his first full season as a professional in 2007 against Hampshire, an innings in which Denly carried his bat.

[89] Denly has been described as an "occasional"[32] leg-spin bowler with a style of bowling which is best suited to limited-overs cricket - his approach has been described as "he stands tall and brings the ball down with plenty of over-spin to pitch near the batsman’s toes and go under flailing bats".