The 23-year-old was left with critical head injuries after the attack on Sheepcote Street on Friday.
He was walking beside a canal at around 6.20pm when he was approached by two men and a woman.
One of the men kicked the victim in the face and body, before stealing some of his possessions, according to West Midlands Police.
All three then ran away in the direction of Birmingham’s International Convention Centre.
The victim was rushed to hospital. His head injuries were so severe he had to undergo emergency surgery.
He remains in a critical condition in hospital.
The three suspects are all described as Asian and in their early 20s. The woman was wearing a fawn scarf around her head.
“It is terrible to hear that a young man who went out to socialise on a Friday evening and has ended up fighting for his life in hospital,” said Detective Inspector Vanessa Eyles.
“We urgently need to find out the identities of the three suspects and are appealing to people to come forward with any information that will help us to identify them.”
Anyone with information is urged to call 101 or to contact Crimestoppers anonymously on 0800 555 111, giving crime reference 20BW/267213V/18.