The three joined the TMC in the presence of its supremo and chief minister Mamata Banerjee at a programme here.
Speculations over the trio joining the TMC gained momentum after they met Banerjee at state secretariat 'Nabanna' last month.
Mollah, a sitting MLA and a former state committee member of CPI-M, was expelled from the party in 2014 for anti-party activities and had floated Nayvichar Manch.
Mollah was the Land and Land Reforms minister in the Left Front ministry.