US Central Command said C-130 transport aircraft had made "multiple" drops of supplies provided by Kurdish authorities in Iraq.
US air strikes have helped push back ISIL in the town near the Turkish border.
Correspondents say the airdrops are likely to anger key US ally Turkey.
The drops of supplies provided by Kurdish authorities in Iraq were "intended to enable continued resistance against Isil's attempts to overtake Kobane," CentCom said in a statement. ISIL is also referred to as IS and Isis.
All the aircraft involved had returned safely, it added.
CentCom says US forces have conducted more than 135 air strikes against ISIL in Kobani.
"Combined with continued resistance to Isil on the ground, indications are that these strikes have slowed Isil advances into the city, killed hundreds of their fighters and destroyed or damaged scores of pieces of Isil combat equipment and fighting positions," its statement said.
However, it added that ISIL fighters continued to threaten Kurdish forces' ability to resist and hold the city. "Kobane could still fall," it said.
On Sunday, Turkish President Recep Tayyip Erdogan said he would not allow Kurdish fighters to receive any transfers of American arms.
ISIL militants control territory straddling Syria and Iraq. Kobane is one of their strategic objectives, and fierce fighting has raged in the town for weeks, forcing the evacuation of most of its civilian inhabitants.
Turkey has resisted calls to help the Kurds fighting in Kobane, describing them as terrorists like the Kurdish militant group the PKK.
Turkey has faced a decades-long insurgency by the PKK, which is regarded as a terrorist group by the US and other allies of Turkey.