A missing nine-year-old boy with autism has been rescued shivering and exhausted from Melbourne’s Maribyrnong River more than two hours after he vanished.

He had disappeared from the suburb of Braybrook in Melbourne’s west at about 5.30pm on January 2. He was spotted by a member of the public struggling in the river two hours later.

He was plucked from the water “exhausted and unable to walk” a short time later by First Constable Jesse Kozak, who said if he hadn’t been noticed by a nearby resident “the consequences would have been tragic”.

“The child was not only struggling in the water, we soon realised he was also struggling to communicate and was unable to shout for help,” he said.

 “He was shivering in the water and when we managed to rescue him, he was exhausted and unable to walk."

First Constable Jesse Kozak carrying the boy. Photo / Victoria Police

“We were shocked when we realised he was reported missing in Braybrook and had managed to travel down the river to Avondale Heights.”

The boy was rescued near Peerless Ct in Avondale Heights about two and a half kilometres from where he was last seen.

He was carried about 1.5km uphill to waiting paramedics.

First Constable Kozak said he wanted to thank the person who alerted police to the struggling boy.