Former Mozambique President Armando Guebuza. Image: Stephanie de Sakutin/AFP
Ndambi Guebuza, the oldest of Guebuza's four children, was picked up from his home in the capital Maputo.
Maputo-based independent STV channel said he was arrested in connection with a government debt which plunged the country into its worst financial crisis.
"He is one of the eight arrested by order of the Attorney-General," a judiciary source who asked not to be named, told AFP.
Mozambican authorities this week arrested seven other suspects, including businessmen and intelligence officials in connection with the debt scandal.
The scandal came to light in 2016, a year after the ex-leader Guebuza left office following a 10-year tenure.
It is alleged that while he was still in power, the government in Maputo had taken out loans amounting to $2 billion to buy a tuna-fishing fleet and surveillance ships, but hid the transaction from parliament and international donors.
An independent audit found that a quarter of the loan amount was diverted, and unaccounted for.
When the debt was revealed, Mozambique — which is one of the world's poorest countries and relies on donor aid — was plunged into the worst financial crisis in its history as donors froze contributions.
The United States alleges at least $200 million was spent on bribes and kickbacks, including $12 million for former finance minister Manuel Chang, who allegedly signed off the debt.
Chang, 63, was arrested at Johannesburg's O.R. Tambo International Airport on December 29 on a US extradition request over his alleged involvement in the fraudulent loans to state firms.
He was denied bail on Thursday.
Ndambi Guebuza, who is a businessman, is alleged to have received $9.7 million in bribes, according to a US indictment.