Namal Rajapakse was remanded into custody for accepting more than $500,000 from an Indian company, police told a Colombo judge.
Colombo Fort Magistrate ordered Rajapakse, a lawmaker from an opposition party faction loyal to his father Mahinda, to be kept in custody until July 18 to allow the police's Financial Crimes Investigations Division to conduct their enquiries.
There was no immediate comment from the former first family over 30-year-old Namal's arrest.
The ex-president's younger son, Yoshitha, is already facing similar money laundering charges over dealings at his private television channel, Carlton Sports Network.
In April last year, authorities arrested Mahinda Rajapakse's younger brother Basil, who was a government minister under his sibling.
The ex-president and his relatives controlled nearly 70 percent of Sri Lanka 's national budget during his rule that ended in January 2015, when he was defeated at the polls by his former ally Maithripala Sirisena.
The new president has vowed to investigate allegations that members of Rajapakse's family siphoned off billions of dollars from the country during his nearly 10-year rule.