Mitchell, whose previous clubs include Cricklade Town and Highworth Town, is an imposing shot stopper who has demonstrated much quality during his time in the Hellenic League.
He made a big impression during his first stay at Cinder Lane before departing with manager Paul Braithwaite to Wootton Bassett in the summer of 2014.
Returned to Fairford midway through the 2015/16 season and was a regular during the title winning 2016/17 campaign.