Early career Watmore started his career at
Manchester United, but was released at the age of 12. He joined
Altrincham in their youth team at the age of 16. Watmore had spells on
loan at
Northern Premier League Division One North clubs
Clitheroe and
Curzon Ashton in early 2012. He scored 14 goals for Altrincham in the 2012–13 season. He made his debut for the Sunderland first team on 5 January 2014 as a 60th-minute substitute for
Ji Dong-won in a 3–1 home win against
Carlisle United in the third round of the
FA Cup. On 31 January 2014, Watmore joined
Scottish Premiership club
Hibernian on loan for the rest of the
2013–14 season. His first goal came on 15 March 2014 in a 3–1 defeat away to
Partick Thistle. Watmore left Hibernian at the end of the season. On 29 May 2015, Watmore was named the
U21 Premier League Player of the Season, after scoring 11 goals in 19 matches in the competition. Watmore made his league debut for Sunderland on 15 August 2015, coming off the bench to score a late consolation goal with a scuffed volley into the bottom-left corner in a 3–1 home loss to
Norwich City. He signed a new four-year contract with Sunderland on 22 November 2015. Watmore returned from two months out with an ankle injury on 16 April 2016 as a half time substitute away to Norwich City, and scored the third goal in Sunderland's 3–0 victory, a result which brought the team to within a point of Norwich in the relegation battle. Watmore was ruled out for the remainder of the a
2016–17 season after suffering cruciate knee ligament injury during Sunderland's 2–1 home win over
Leicester City on 3 December 2016. It was announced on 17 June 2020 that Watmore would be leaving Sunderland, bringing to an end his 7 years at the club.
Middlesbrough On 17 November 2020, Watmore signed for
Middlesbrough on a short-term deal until January 2021. He scored his first goals for Middlesbrough when he scored twice in a 2–1 win against
Swansea City on 2 December 2020. Watmore continued his goal scoring with two on 12 December in a 3–0 win against
Millwall. On 7 January 2021, Watmore signed a new two-and-a-half-year deal at Middlesbrough. Watmore's performances earned him the championship player of the month for December. Watmore was Middlesbrough's top scorer for the
2020–21 season, with nine goals.
Millwall On 31 January 2023, Watmore signed for
Millwall for an undisclosed fee. On 19 May 2025, the club announced the player would be leaving in June when his contract expired.
Rotherham United On 2 February 2026, Watmore signed for
Rotherham United. ==International career==