The former TMC leader, known for his organisational skills, joined the BJP in the presence of Union minister Ravi Shankar Prasad and party general secretary Kailash Vijayvargiya
"Today a veteran public figure and political leader Mukul Roy has joined BJP," Union Minister Ravi Shankar Prasad said at a press conference.
He had described BJP as a non-communal party and said that the TMC would not have tasted success without the backing of the saffron outfit at the national level in its initial years.
Roy was last month suspended from the TMC for six years for indulging in anti-party activities after he announced that he would quit the party.
Roy was also removed as the TMC vice-president after the party decided to restructure its committee.
He was earlier removed as the party's points man for Tripura, where the TMC made inroads till its members switched over to the BJP earlier this year.