The value of the seized goods, which included Hermes and Louis Vuitton bags, is yet to be ascertained due to the scale of the confiscation, Bernama reported.
Najib was deeply unpopular and facing allegations of corruption and misappropriation of money from a state fund, the Malaysia Development Berhad (1MDB). His coalition party, Barisan Nasional, led the country since its independence 61 years ago. Mahathir had pledged to hold Najib accountable.
At a press conference on Thursday, Mahathir had said the police had enough reason to raid Najib's house.
"We have instructed investigation into all crime cases, no matter who is involved. If there is a case against them, we will take action," he said.
Six properties were searched in total in relation to reopened probe into the 1MDB scandal, the state investment vehicle from which Najib is accused of siphoning off billions of dollars. Najib has denied any wrongdoing.
Documents relating to the 1MDB scandal were retrieved in raids conducted on six properties, including four homes, the former prime minister's official residence and his office in Putrajaya, according to Commercial Crime Investigation Department (CCID) director Amar Singh Ishar Singh.
On Thursday Najib's lawyer, Harpal Singh Grewal, told reporters that he understood that the items had been seized in order to advance an investigation under the Anti-Money Laundering and Anti-Terrorism Financing Acts, Bernama also reported.
Najib and his wife, Rosmah Mansor, are on an Immigration Department watch list, and banned from leaving the country.