Mitchell made his Wales debut on the successful summer tour of America and Canada in 2009 under the guidance of forwards coach Robin McBryde - who took charge whilst Gatland was on British & Irish Lions duty - and won his most recent cap making his home debut against Samoa in the 17-13 win last November.
The call-up also means the tight-head will join fellow props Paul James and Adam Jones (Ospreys) and John Yapp (Blues) on the two-Test tour of New Zealand which immediately follows the home clash with the World Champion Springboks.
"Craig knows all about our international environment and has been training with us all week in any case, so his transition will be pretty seamless," said McBryde.
"His promotion is a continuation of our selection and development policy and having been blooded in USA and Canada and against Samoa this Autumn he won't let anyone down if called upon.
"He will primarily cover Adam Jones' side of the scrum and, with Paul James pretty comfortable on both sides and John Yapp also with some experience on either side, we think we still have a good balance there.
"Our front row should be an experienced unit, with the likes of Adam and Matthew (Rees) both returning from the Lions tour in the summer with enhanced reputations, but the Springboks are by no means short on experience there themselves and with Smit leading from the front it should be quite a battle.
"We are also pretty familiar with the talents of BJ Botha at Ulster and we will all be watching how the Ospreys go this weekend, with a particularly interesting battle going on between Paul James and CJ van der Linde, who could well be up against each other again in international colours the following week.
"That first scrum in Leinster could provide some interesting clues as to what may lie ahead, although there is no doubting the intensity of international competition will be a new level again.
"Whatever happens in Ireland, facing the World Champions in Cardiff will definitely be a step up, but we are all backing the Ospreys to lay down a marker, to put in a performance against Leinster, claim the silverware and bring some momentum into camp when they join up with us on Monday."
Wales have also confirmed Scarlets hooker Ken Owens has been released to play for the Barbarians against England at Twickenham this Sunday.
Craig MITCHELL (OSPREYS - Cap No 1,068)
DoB: 03.05.86. 6'1" / 1.85m. 17st 2lbs / 109kgs
International record: 3 caps (W 3)
Scott ANDREWS (CARDIFF BLUES)
DoB: 01.08.89. 6'2" / 1.88m. 18st 1lb / 115kgs
International record: Uncapped