It would mark the first time Israel has allowed a UN agency to get aid to Gaza via the port since announcing it would open earlier this month.
"Eight World Food Programme trucks of flour entered the Gaza Strip from the Ashdod port today," the army said in a statement.
On April 5 Israel said it would use the Ashdod port, just north of Gaza, to deliver aid to the Palestinian territory which the UN and aid agencies have repeatedly warned is on the brink of famine.
"The trucks underwent a thorough security inspection at the Ashdod port," the Israeli army said. "They were then admitted into the Gaza Strip via the Kerem Shalom Crossing."
On Tuesday the United Nations agency for Palestinian refugees, UNRWA, said there had been "no significant change" in the amount of humanitarian aid entering Gaza, even after the International Court of Justice ordered Israel to allow in more.