Harvey Sayer started his football journey as a five-year-old at Bungay Town FC before being scouted by Norwich City, aged eight. He progressed from the Player Development Centre into the elite before gaining a place in the academy. However, he was released by the Canaries at 12 but was scouted by Colchester United, playing for Suffolk County Schools. 

Colchester initially wanted to give him a six-week trial but after a couple of weeks, offered him a contract on his 14th birthday in January, 2017. While playing for Colchester, he was scouted by England and in February 2018, played for the Young Lions' under-15 side against Belgium. 

He spent some of the 2019/20 season on loan at Maldon and Tiptree, making two appearances.

Sayer, who also had once had a trial at Wolves, scored in Colchester’s first three Under-18s games in the 2020/21 season and impressed for the Under-23s recently. He made his first team debut in the Papa Johns Trophy against West Ham in September 2020 and signed his first professional contract in January 2021.

On 21st October 2021 he joined Needham Market of the Southern League Premier Division (Central) on loan. In February 2023 he was loaned to Stowmarket Town of the Isthmian League.