The 24-year-old has some League One experience having played 15 games for Brentford during the 2006-07 campaign and has spent the last 18 months at Fisher.
Tomlin told the Glovers' official website: "I'll get my head down and concentrate and make sure that I have a place for the start of the season.
"All the boys have made me feel welcome and it's a nice club to be honest, so it was an easy decision for me to make."