Governor K. Sankaranarayanan administered the oath of office to Jadhav at a brief function in Raj Bhavan here.
Jadhav, 57, was on Wednesday replaced by Sunil Tatkare, who quit as water resources minister, as president of the NCP's state unit.
Incidentally, both Jadhav and Tatkare hail from the state's coastal Konkan region, which is regarded as a stronghold of opposition Shiv Sena.
Tatkare's appointment as the new NCP chief is considered crucial in view of the ensuing assembly elections, according to political analysts. Polls in the state are due within three months.