The 26-year-old former Ivybridge Community College pupil has played for Exeter, Bedford, Newcastle, Cornish Pirates, Ealing and Esher.
He arrives at Brickfields from Esher, where he made 18 starts and eight replacement appearances in National One last season.
Bedford, who played for Devon under Graham Dawe earlier in his career, wanted to return to the West Country after two years living in London.
He started his career at Exeter while still at school and made 44 appearances for them before joining Championship side Bedford.
The centre, who is a qualified tree surgeon, was a regular starter for the Blues for one-and-a-half season before earning the chance to play in the Premiership for Newcastle. He then joined the Pirates before moving to Ealing for their debut season in the Championship.
Dawe, who confirmed Bedford will be part-time at Albion, said: “He wanted to come back to Devon. He’s got a young family and he wanted to bring them back down here and play some good rugby.
“He’s looking forward to joining Plymouth, getting stuck into pre-season and making a fresh start in Devon.”
The Albion boss added: “Tom is a player who certainly has the ability to break defences with his power and can play 12 or 13.”
Dawe has already said he sees Australian Marc Koteczky as a 12, but he is keen to have three specialist centres backed up by the likes of Ethan Ford and Cameron Setter, who can also play there.
Bedford’s arrival, which takes Albion’s National One squad up to 10 players, is set to be followed in the next few days by that of Moseley forward Nile Dacres and Cornwall winger Jon Dawe, who have both agreed to join the club.