29-year-old Baldwin, who made nine appearances for the Grecians last season on loan from Southend, joined the club in the summer of 2012.
He began his career at Chelsea before spending ten years at Colchester United and making over 200 appearances.
Baldwin spent time out on loan at a number of clubs including Bristol Rovers where he partnered Danny Coles
at the heart of the Gasheads' defence - a partnership that is likely to be rekindled during the coming season.
He then made the move to Southend who loaned the experienced centre back to St James Park during the climax to the 2011/12 season.