It is thought Yemen is a few months away from running out of food for its whole population.
Oxfam is warning the amount of food being imported has been below half the amount needed since August, because of ongoing conflict with Saudi Arabia.
The charity says Yemen is being "slowly starved to death" and that it's "not by accident".
Oxfam said: "Deadly clashes and airstrikes have forced over 3.1 million people to flee their homes since March 2015.
"As many as 21 million people are in need of humanitarian assistance, a shocking 82% of the population, and 14.1 million people cannot afford enough food for their families."
Jim Clarken, Oxfam Ireland Chief Executive, said: "Yemen is being slowly starved to death. First there were restrictions on imports – including much need food – but when this was partially eased the cranes in the ports were bombed, then the warehouses, then the roads and the bridges. This is not by accident – it is systematic.
"The country’s economy, its institutions, its ability to feed and care for its people are all on the brink of collapse.
"There is still time to pull it back before we see chronic hunger becoming widespread starvation. The fighting needs to stop and the ports should be fully opened to vital supplies of food, fuel and medicine."