Chief Minister Harish Rawat welcomed Bhandari into the party fold soon after he and his supporters joined the Congress in the presence of senior party leaders, including state unit chief Kishore Upadhyay.
Rawat said Bhandari's entry will strengthen the party ahead of the 2017 Assembly elections.
Bhandari had resigned as MLA on June 10, a day before polling was held for the lone Rajya Sabha seat on June 11.
He though had not mentioned any reason while tendering his resignation to Vidhan Sabha Speaker Govind Singh Kunjwal.