The victim, in his 20s, was left with a “nasty head injury” after he was targeted by a group of people in Blackpool town centre in the early hours of Tuesday morning.
Video footage posted on social media appears to show the young man being stamped on and dragged down a set of steps before being left on the pavement in Bank Hey Street.
Lancashire’s deputy police and crime commissioner Chris Webb shared the footage on his Facebook page, saying: “This is vile and disgusting. They bring shame on our town.”
Police say the ambulance service was called at about 5.30am and the man was taken to hospital for treatment.
Officers are now urging anyone who witnessed the incident or who has information to get in touch.
Sergeant Sarah Moyes, of Blackpool Police, said: “This was a sickening attack and the victim has been left with a nasty head injury.
“We have made two arrests but our enquiries are very much ongoing and we would like to speak to anybody who witnessed the assault or who has information about what happened.
“If you can help with our enquiries please get in touch as soon as possible.”
Homeless charity The Albert Project said it tracked down the victim, known as Jamie, who had been “asleep minding his own business” when he was set upon.
The project posted an update on Tuesday afternoon saying he had been given somewhere to sleep and was regularly being checked on in case he had a concussion.
It added: “I know a lot of you have seen the disgusting and very disturbing video.
“We are absolutely shocked by this behaviour and the chairman has been and found him.
“He has been supplied with a new sleeping bag, new hoodie, socks and underwear clean clothes, toiletries, snacks and he has been given a KFC.”
Anybody with information about the incident can contact police on 101, quoting log number 172 of 24 September.