Yoshitha Rajapaksa, the second son of ex-strongman Mahinda was, arrested and quizzed this morning by the police's Financial Crimes Division (FCID) at the Sri Lankan Navy headquarters, a navy spokesman said.
He and four others have been arrested on money laundering allegations, police said in a statement.
Yoshitha, who is a navy officer, is the first immediate family member of former President Mahinda to be arrested since his shock defeat at the hands of Maithripala Sirisena in the polls last year.
He was quizzed in connection with TV channel Carlton Sports Network (CSN) which had close links with the Rajapaksa sons.
CSN was controversially handed over Sri Lankan cricket's television broadcast rights under the Rajapaksa regime. The broadcast rights had been the preserve of the state television until then.
Nishantha Ranatunga, who was CSN's CEO, was also among those arrested. He was also the Secretary of the Cricket governing body.
Sri Lanka witnessed a huge political change in the beginning of last year when Sirisena trounced Rajapaksa in the January 8 presidential race, ending his 10-year-rule.
Rajapaksa in August tried to stage a dramatic comeback as prime minister as Sri Lanka voted to elect a 225-member Parliament.
However, Rajapaksa's hopes were dashed as Ranil Wickremesinghe's United National Party (UNP) won a closely-fought election to form a national unity government.