"The ministry congratulates the Beast on his becoming a South African citizen, as well as the South African Rugby Union for acquiring his services," sports minister Makhenkesi Stofile said in a statement.
He now qualified for selection to the national team.
Mtawarira was born in Zimbabwe and moved to South Africa shortly after finishing school. He made his debut for South Africa in 2008.
In November last year Stofile accused sports federations of not respecting South African laws by choosing foreigners to represent national teams.
In an advert placed in several newspapers, the ministry said it was not good enough for Mtawarira to have been issued with an exceptional skills visa.
It accused the SA Rugby Union (Saru) of "vulgarising" the concept of exceptional or scarce skills. The ministry said sports federations could apply for work permits for a limited number of foreign players or administrators, but only if such applications were compellingly motivated.
Saru met with the sports department to sort out Mtawarira’s eligibility to play for South Africa, but the issue was not laid to rest.
Earlier this month rugby selectors were told Mtawarira would not be eligible to play for the national side until he became a South African citizen. – Sapa