A CBI spokesperson said that Das was allegedly helping the illegal operations of Saradha group in South 24-Parganas district in West Bengal.
He was arrested this morning by CBI sleuths, she said.
Das who had gone into hiding since August 2014 after the agency summoned him for examination, would be produced in the court later during the day.
Earlier, CBI had arrested Sen and another close aide Debjani Mukherjee both of whom were now in jail custody.