CFA crews were alerted to a fire on the island, last night at 9.50pm.
Goat Island, a Murray River island, is located close to the Victorian town of Swan Hill where a member of the public spotted the fire and notified authorities.
The uninhabited Goat Island was not accessible for the CFA or NSW Rural Fire Service via a road or bridge.
An SES unit attended and ferried CFA and NSW firefighters and equipment across the water to the island.
Operations Officer Robin McNally praised the other agencies who attended, particularly SES.
"We couldn't have done it without them," Mr McNally said.
He said the cause of the fire was still being investigated.
"It's possible the fire was caused by fireworks but we don't know at this stage."
The fire was contained within two hours and will be monitored in the coming days. Helitak 335 was used to fire bomb the fire and is expected to be used further if hotspots are found.
The incident was attended by four CFA brigades, with six appliances, one NSW Rural Fire Service Brigade and one SES unit.