Governor Syed Ahmed administered the oath of office and secrecy to Das at the Birsa Munda Football Stadium here.
Nilkanth Singh Munda, Chandreswar Prasad Singh, Louis Marandi (all BJP) and Chandraprakash Choudhary (Ajsu party) were also sworn-in as cabinet ministers.
Jharkhand has a maximum limit of 12 ministers, including the chief minister.
Dense fog in New Delhi led Prime Minister Narendra Modi and BJP President Amit Shah to cancel their visit to Jharkhand to attend the ceremony.
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After being elected as the BJP's legislature party leader, Das had staked claim to form government on December 26 at the head of BJP-Asju alliance.
Das joined the BJP as a worker and then gradually rose through the party ranks before getting the first break when he was nominated as party candidate from Jamshedpur (East) in the 1995 Assembly elections.He went on to win the seat five times.
He held portfolios of finance, labour and urban development during his stint as cabinet minister.