Keith Watson, Michael Gardyne and Brian Graham will all not be offered new contracts at Tannadice at the end of the current season.
Defender Watson, who made 152 appearances for the club, joined Hibernian on loan in January.
Gardyne scored three goals for United, but has spent the past two seasons on loan, at Kilmarnock and then Ross County. He recently criticised his parent club for their lack of communication.
Graham scored seven goals in 37 appearances after joining from Raith, but has spent this season at St Johnstone.