In April, UN aid officials said the town was suffering dire shortages of food, clean water and medicine.
A 48-hour ceasefire for the town, which lies south of Damascus, came into force early on Wednesday.
Vaccines, baby milk, medicine and nutritional goods were being delivered, the UN`s humanitarian arm said.
In April, the UN said at least 4,000 people were besieged in the town by Syrian government forces.
Darayya`s electricity supply was cut off more than three years ago.
Speaking at the time, UN emergency relief co-ordinator Stephen O`Brien said the Syrian government had ignored "countless" requests for aid to be allowed in.
An aid convoy was blocked from entering the town last month, despite all involved parties agreeing aid could be delivered.
Russia`s defence ministry said on Wednesday it had agreed a "regime of calm" with the Syrian authorities for 48 hours to allow for the distribution of humanitarian aid in Darayya.
The suburb borders a military airport used by Russian planes in support of the government of President Bashar al-Assad.
Syria conflict: First aid for Darayya since 2012
02 June 2016
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The besieged Syrian town of Darayya has received its first aid convoy since November 2012, according to the country`s Red Cross.
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