G Baskaran (Sivaganga), Sevvoor R Ramachandran (Arani), Nilofer Kabil (Vaniyambadi) and P Balakrishna Reddy (Hosur) were sworn-in at the Raj Bhavan here.
Governor K Rosaiah administered them the oath of office and secrecy in the presence of Chief Minister J Jayalalithaa.
On Monday, Jayalalithaa and 28 others were sworn-in and later in the day she announced expanding her cabinet and included four more, all new faces.
Baskaran is Minister for Khadi and Village Industries Board while Ramachandran has been allotted Hindu Religious and Charitable Endowments.