The 80-year-old Singh, who is the Leader of the Upper House, was recently elected a member of Rajya Sabha from Assam for the fifth consecutive term.
Congress president Sonia Gandhi and party leaders Ahmed Patel, Motilal Vohra and Rajiv Shukla were among those present on the occasion.
Mr. Singh, who took oath in the name of God, told reporters that “It is a great opportunity for me to re-dedicate myself to the service of the people of Assam.”
Lok Janshakti Party president Ram Vilas Paswan, SP leader Ram Gopal Yadav and a number of Rajya Sabha members were present at the function.
Another Congress member from Assam Santius Kujur also took oath today.
The election to the two Rajya Sabha seats from Assam had taken place on May 30 with Congress winning both the seats.