The 31-year-old tighthead, who has earned 15 Test caps, joined the Dragons from Cardiff Blues in 2016.
Neath-born Mitchell – who has also played for Ospreys and Exeter Chiefs – will bolster James Lowes’s side for the final run-in and he is named on the bench for this afternoon’s league game at Bedford Blues.
Despite the cold weather this week, the fifth-placed hosts are confident the game will go ahead.
The Goldington Road pitch has been covered with frost sheets since last Friday and volunteers have been asked to clear snow this morning.
Lowes has made four changes to his side, who sit third, after Sunday’s 22-12 defeat at Cornish Pirates.
Scrum-half Alex Davies was injured in that contest so is replaced by Will Homer, who played the majority of last week’s game at No 9.
Callum Irvine gets the chance to play at fly-half which allows Pete Lucock to revert back to centre to replace Tom Casson, who is among the replacements.
Prop Charlie Beech returns having missed last week through concussion while Matt Smith starts in the second-row for Ben West.
Rotherham Titans’ game at Ealing Trailfinders has been postponed due to snow and will be played next Saturday.