It happened in Lower Town Street, near Bramley Shopping Centre, at 4.30am this morning (Saturday May 15).
Police received a call reporting that a man was being attacked by a group of males.
Officers believe the victim, a 36-year-old man, was kicked and stamped on while he was on the ground.
He was treated by paramedics and taken to hospital. His injuries are not believed to be serious.
Police arrested a 21-year-old man and two teenage boys, aged 15 and 16, who were nearby.
They remain in custody.
Bramley Shopping Centre was cordoned off as crime scene investigators conducted their enquiries. The cordon was lifted by 9am.
Sergeant Simon Hartley, of the Leeds West Neighbourhood Policing Team, said: “At this time we are working to establish the motivations behind this attack and are keen to speak to anyone who has any information which could help our investigation.
“We will be stepping up patrols in the area and reviewing CCTV from the locality.
“I would urge anyone with information about this assault to please contact the police.”
Information can be passed to the police via 101 or online using the 101 Live Chat facility on the West Yorkshire Police website, quoting crime reference 13210239757.
There is also the option to contact independent charity Crimestoppers anonymously on 0800 555 111.