Tamil Nadu Police has assisted its Kerala counterpart to nab the accused.
Radhakrishnan would be taken to Kerala to be produced in court, police said.
Biju had been absconding ever since his estranged wife Saritha Nair was arrested on June 3 in connection with the solar panel fraud case.
The duo had allegedly cheated several people of crores of rupees, promising to install solar power solutions and share in wind mill farms.
The case took a political turn after media reported telephone conversation between two staff of the Chief Minister's office, who were removed last week.
Ruling out his resignation and a judicial probe, Chandy charged the Opposition with creating a 'smokescreen' over the issue without any substance.