Legzdins had a year remaining on the contract he signed last summer when he moved to Brisbane Road from Derby.
The 28-year-old endured a injury-plagued 2014/15 campaign. He only made just 13 appearances for the O’s after struggling with a shoulder injury for a large chunk of the season.
Legzdins started as Orient’s first choice goalkeeper but failed to make an appearance after suffering his injury during the Boxing Day victory against Crawley.
A statement on the club’s official website said: “Leyton Orient would like to thank Adam for his efforts at the club and wish him well for the future.”