The Zimbabwe-born Mtawarira, nicknamed "Beast" and a crowd favourite for the Durban-based Sharks in Super 14s, has 22 test caps for the Springboks but was in international limbo because he did not have a South African passport.
He was legally resident in South Africa and fulfilled the eligibility criteria of the International Rugby Board but South African rugby officials had been instructed earlier in the month not to select the 24-year-old prop because of the passport situation.
Mtawarira has now been granted South African citizenship on residency grounds and after government intervention and was immediately eligible for a Springboks recall.
Francois Hougaard was also drafted back into the squad, which contained 21 players involved in Saturday's 55-11 win over Italy.
Five players who were involved in the earlier tests against Wales, France and Italy were also selected after coming back from rest or injuries, including vice-captain Victor Matfield, lock Danie Rossouw, backrower Ryan Kankowski, prop CJ van der Linde and fullback Zane Kirchner.
Among those unavailable for selection due to injury are scrum half Fourie du Preez, wingers JP Pietersen and Odwa Ndungane and hooker Bismarck du Plessis.
The Springboks play the All Blacks at Auckland on 10 July and Wellington on 17 July before facing Australia at Brisbane on 24 July.
South Africa squad for Tri Nations: Backs: G Aplon, J de Jongh, J de Villiers, J Fourie, B Habana, F Hougaard, B James, R Januarie, Z Kirchner, W Olivier, R Pienaar, M Steyn. Forwards: A Bekker, B Botha, BJ Botha, S Burger, J du Plessis, R Kankowski, F Louw, V Matfield, T Mtawarira, D Potgieter, C Ralepelle, D Rossouw, J Smit (captain), P Spies, G Steenkamp, CJ van der Linde.