Adam Marriott joined Cambridge United's centre of excellence as a scholar aged 15 having previously been with Norwich City. He lives in Brandon and plays as a central midfielder / centre-forward. He played for United's CRC side in the Ridgeons League during 2006/7. He scored 11 goals in 59 appearances for United.

He moved to Cambridge City in January 2013. He scored 41 goals in 2013/14. He was the league’s top scorer. The 23-year-old striker was given a special award for breaking the club’s individual scoring record for one season. He was also handed the BBC Radio Cambridgeshire Player of the Season award and the first-team Players’ Player award.

He joined League Two side Stevenage on 8th July 2014 for a five figure fee.

He was released in May 2016 having made 22 appearances for Stevenage scoring three goals.

On 28th June 2016, Marriott signed a one year contract with Conference side Lincoln City. After they won promotion to the Football League, Marriott turned down a new contract to be closer to his Cambridge home, signing for Royston Town. After a short spell with Boston Town, he moved to Kings Lynn on 9th October 2018 signing a two year contract. He played and scored as Kings Lynn won promotion to the National League (North) in 2018/19 after finishing second in the Southern League and winning the play-offs against Warrington Town (Northern League) on 11th May 2019. The 2018/19 season saw him win the Southern League Golden Boot after scoring 24 goals in 33 league games for Lynn, as well as winning the club’s player of the year award.

His form for Lynn in the National League North in 2019/20 (25 goals in 23 games) resulted in speculation on 7th January 2020 linking him with a return to Stevenage.

On 17th June 2020 it was confirmed that Lynn were winners of the National League South, on a points per game basis due to the premature ending of the season because of Covid-19, and would be promoted into the National League.

On 9th April 2021 he left Kings Lynn to join National League rivals Eastleigh on a permanent basis, having scored 65 times in 99 appearances for the Linnets. He moved to Barnet in July 2021 and to Bromley in June 2022. He scored 17 goals in 36 appearances for Barnet in 2021/22.

Bromley were promoted to the Football League at the end of the 2023/24 season via the play-offs but Marriott played just three games that season and ended the campaign on loan to Boston United. He then signed for Boston on a full-time deal in June 2024.