The Paris-based medical humanitarian organization said the cargo plane carrying 12 tons of drugs, surgical supplies and two dialysis machines was turned away three times and diverted to the neighboring Dominican Republic.
More than 30 countries have rushed relief to Haiti since Tuesday's devastating earthquake, choking the small airfield operated by U.S. Air Force air traffic controllers.
"We cannot accept that planes carrying lifesaving medical supplies and equipment continue to be turned away while our patients die," said Rosa Crestani, a MSF medical coordinator at a Port-au-Prince hospital, said in a news release.
Medical teams for dozens of countries were overwhelmed by the casualties caused by January 12 earthquake that is believed to have killed up to 200,000 people.
"It is like working in a war situation," Crestani said. "We don't have any more morphine to manage pain for our patients."
On Sunday, an MSF plane carrying an inflatable surgical hospital was diverted to the Dominican town of Samana, from where it would take 24 hours to get to Port-au-Prince.
MSF doctors said five of their Haitian patients died at one Port-au-Prince hospital for lack of medical supplies.
"I have never seen anything like this," said Loris de Filippi, emergency coordinator at another Haitian hospital.
"Today, there are 12 people who need lifesaving amputations at Choscal Hospital. We were forced to buy a saw in the market to continue amputations," she said.