The teenage boys, aged 16, 15 and 13, have been charged with robbery and wounding with intent. The 15-year-old has also been charged with possession of an offensive weapon, namely a 13-inch knife, in a public place, and possession of cannabis.
The incident happened in the early hours of Friday morning, January 3, at around 4.40am, in the square outside Victoria Shopping Centre. The boys were arrested on Skipton Road at around 5.20am.
A North Yorkshire Police spokesperson said: "The victim is now recovering following surgery, but will have life-changing injuries."
The man was taken to hospital with injuries to his face, back and leg.
Superintendent Steve Thomas, Harrogate Commander, said on Friday: "This is clearly an extremely serious incident, and residents will naturally feel concerned about what has happened. However, incidents like this are very rare in our town. Thanks to a fast response local officers last night, three suspects have been arrested, and a police investigation is well underway.
"You can expect to see increased patrols in the town centre in the coming days - officers from the Neighbourhood Policing Team will be in the area to provide extra reassurance to residents and businesses. Please do speak to them if you have any concerns.
"It goes without saying that the carrying of knives and other weapons is unacceptable and these additional patrols will be using appropriate stop and search powers to ensure anyone found in possession of weapons is arrested and put before the courts."
Anyone with any information about the incident or anyone who witnessed the attack should contact North Yorkshire Police on 101, quoting reference 12200001239.