Sarma was chosen as the leader of the BJP’s legislative party in the State during a meeting held at the Library Auditorium in Guwahati today.
The swearing-in ceremony will be held on Monday, sources added.
Earlier in the day, Sonowal submitted his resignation to Governor Jagdish Mukhi.
The BJP won a second straight term in the recently concluded Assembly polls in the State.
In the 126-seat Assembly, BJP won 60 seats while its alliance partners Asom Gana Parishad (AGP) won nine seats and United People's Party Liberal (UPPL) won six seats.
On the other hand, Congress won 29 seats while All India United Democratic Front (AIUDF) secured 16 seats. Bodo People's Front (BPF) had won four seats.
Sarma, who switched to the BJP from the Congress six years ago, is credited as the architect who brought the northeast States within the party's grasp.
