The incident happened in Designer Touch Stylists in Farthing Grove, Netherfield on Monday (5/8) at about 3.20pm.
Three men entered the shop, one of whom was armed with a weapon, and attacked the boy.
The victim sustained three stab wounds, one to the chest, one to the arm and one to the leg.
He was taken to hospital for treatment and has since been discharged.
Investigating officer, Detective Constable Serena Bellis, of Milton Keynes CID, said: “This was a serious assault which left a 17-year-old boy with stab wounds requiring hospital treatment.
“I would also like to appeal to anyone who saw this happen, and in particular anyone who has any mobile phone footage of the incident.
“If you have any details which you think could help our investigation, please call us on 101, quoting reference number 43190240373.”
