He was administered the oath by Madras High Court Chief Justice Indira Banerjee.
He succeeded Maharashtra Governor Ch Vidyasagar Rao, who had been holding additional charge of Tamil Nadu since last year.
It is for the first time that the state has got a full time governor after K Rosaiah retired in August 2016.
Purohit, who got involved into active politics in 1977, has been a Governor of Assam as well.
He was a Member of Parliament from the Nagpur three times, twice as an Indian National Congress member, once as a BJP member.
He was elected as an MLA from Nagpur East constituency in 1978, and was re-elected in 1980 from Nagpur South and became a Minister of State in 1982.
In 1984, he was elected to the Lok Sabha and was re-elected in 1989 on Congress ticket.
In 1996, Purohit was elected to 11th Lok Sabha as BJP's candidate and served as a member of the Parliamentary Consultative Committee on Home Affairs, a member of the Standing Committee on Defence, and a member of the Public Sector Undertaking Committee.
In 2003, he launched his own party called Vidarbha Rajya Party and contested the Lok Sabha elections from Nagpur in 2004. (ANI)