Governor Droupadi Murmu administered the oath of office and secrecy to Soren, in the presence of senior political leaders and chief ministers from across states.
This will be the 44-year-old JMM leader's second stint as Jharkhand chief minister.
Along with Soren, Congress Legislature Party Leader Alamgir Alam, state Congress president Rameshwar Oraon and RJD MLA Satyanand Bhokta were also sworn in as state cabinet ministers at Sunday's event.
In the just-conducted Assembly elections, the JMM- Congress-Rashtriya Janata Dal (RJD) alliance triumphed over the BJP, winning 47 seats in the 81-member House.
Four other MLAs - three from the Jharkhand Vikas Morcha (Prajatantrik) and one from the Communist Party of India (Marxist-Leninist) have also extended their support to the three-party coalition.
Those present at the swearing-in ceremony here include Congress leader Rahul Gandhi, West Bengal Chief Minister Mamata Banerjee and her Rajasthan counterpart Ashok Gehlot.