Chesmain began his career with the Lions and progressed through the academy at Millwall.
The left-sided defender was an ever-present in the under-18s and under-21s, before making the step up to the first-team.
On joining the club, Chesmain told the club`s official website: “Yeah I am very pleased, it is a good chance for me to get first-team football, and at a good standard, so I am really chuffed to be here.
“I spoke with the management at Millwall and they told me that the Gaffer here was a great guy, that he plays a good tempo, and that he likes to play. They told me to give it my best and it took off from there.
“When I arrived here, everyone was really happy and working hard, which just makes me feel welcome.”
The full-back made his debut for the Lions against Bury in November 2015, when he replaced Shane Ferguson in the final 10 minutes of the game, helping his side to a 1-0 win.
The youngster has previously spent time on loan with Welling United in the National League and said that he knows the level well.