"Thirty months of war, high prices for consumer goods and unemployment have had a massive impact on people," MSF said, adding that a "great number of children" suffer from malnutrition.
"Millions of Yemenis who cannot access primary health care (are in a) desperate situation," Ghassan Abou Chaar, head of the MSF mission in Yemen, said in the statement.
Health workers have not been paid for the past 13 months, the organisation said.
Yemen was plunged into civil war in 2015, when a powerful military coalition led by Saudi Arabia joined the government's fight against Iran-backed Huthi rebels.
More From This Section
"It has been shocking to see the terrible impact of this man-made conflict," he said yesterday.
According to the World Health Organization more than 8,650 people have died in the conflict including many civilians.
Another 2,100 people have died of cholera since April as hospitals struggle to secure basic supplies amid blockades on ports and the country's main international airport.
OCHA says more than 11 million children need humanitarian assistance.
According to the United Nations, the conflict in Yemen has left seven million people at risk of famine and an estimated 17 million -- 60 per cent of the overall population -- food insecure.