A UN refugee agency official said the convoy - the first since mid-February - delivered as much as it could in Douma town and left after nearly nine hours.
But the UNHCR said 10 out of more than 40 trucks had not been emptied.
Activists said dozens of people died in air strikes by Syria's army on Monday, despite a supposed five-hour truce.
At least 719 people have been killed in recent weeks, many of them children.
The UNHCR's Syria representative Sajjad Malik tweeted late on Monday that "we delivered as much as we could amidst shelling".
"Civilians are caught in a tragic situation."