The 21-year-old arrives from the Amex Stadium despite interest from a host of League One and League Two clubs, becoming a Glover for the remainder of the campaign.
Able to operate on either wing, in attacking midfield or as a striker, Tilley heads to Somerset for a second spell away from the south coast.
Joining League of Ireland club Cork City in January, the youngster made a lasting impression on the Rebel Army by scoring three and assisting three goals in 28 appearances.
With the Seagulls from the age of 12, he made his senior debut in the Championship aged just 16 in 2015, adding a further two first-team appearances which included scoring the winner against Barnet in the EFL Cup.
Also competing in the EFL Trophy for the under-23s, Tilley amassed a further 10 appearances adding one goal.
Wearing the number 28 shirt during his time at Huish Park, the attacker is eligible for Tuesday night’s National League encounter with Sutton United.