However, the minister did not disclose the date of expansion.
Fadnavis and nine others had taken oath on October 31, after BJP with 122 MLAs emerged as the single largest party in the October 15 election to the 288-member Assembly.
After power-sharing parleys were successful, Shiv Sena joined the government on December 5, when 10 Sena ministers and 10 BJP ministers were inducted, taking the ministry strength to 30. With the latest expansion, the strength will be 42.
The constituents of the BJP-led Mahayuti, which contested the polls jointly with BJP after that party severed its 25-year-old alliance with Shiv Sena ahead of the elections, have been demanding their share after BJP came to power.
BJP had tied up with RPI, Swabhimani Shetkari Paksh, Rashtriya Suraj Party and Shivsangram.
Meanwhile, the minister also announced that the state government will act against sugar factories which fail to make payment to sugarcane growers as per the Fair and Remunerative Price (FRP) fixed by the government.
Action will also be taken against sugar mills starting crushing season without obtaining necessary approvals, he said.