An order was signed by Prime Minister Hun Sen following "some negative information" about the working environment of Cambodian maids in Malaysia, Oum Mean, secretary of state at the ministry of labour, told AFP.
"The government has issued a circular... to temporarily suspend sending maids to Malaysia," he said, without specifying how long the ban would last.
The surprise move comes after campaigns by activists in recent months highlighted dozens of cases of sexual abuse, overwork and exploitation among an estimated 50,000 Cambodian women employed as domestic helpers in the country.
Rights group Tenaganita, which has rescued more than 60 Cambodian maids so far this year, said it was "elated" by the ban.
"We call on all countries in the region to take heed that migrants are not for sale and there can be no compromise on the protection of their rights," the Malaysia-based group said in a statement.
The move was also welcomed by Human Rights Watch, which recently sounded the alarm about Cambodian training centres for prospective maids, an industry they say is plagued by debt bondage, forced confinement and use of underage workers.
"Hun Sen is finally demonstrating concern about the plight of Cambodian migrant domestic workers, but a ban is only a temporary measure," said Jyotsna Poudyal, the group's women's rights research fellow.
"The government should introduce major reforms, in consultation with civil society, to improve regulation and monitoring of labour recruitment in Cambodia so that women can migrate voluntarily and safely," she added.
Oum Mean said the order was signed by Hun Sen on October 15 and the government had informed recruitment agencies and state institutions about the suspension.
But he did not specify which conditions Malaysia would have to meet to get the ban overturned.
Reports of abuse in Malaysia have frequently surfaced in recent years and led Indonesia to stop sending domestic helpers to the country for two years in 2009, prompting a rise in demand for Cambodian workers.