The owner of the salon, in the in the upmarket district of Majorstuen, has been fined 20,000 Norwegian kroner ($1,920) after police raided the premises last week.
“When we got there, there were several people still inside the room. There was a person who worked there,” Morten Reppen of the Oslo police told the country's state broadcaster NRK. “He seemed to understand that this was not allowed.”
As part of Norway's shutdown, gyms, hairdressers and skincare clinics were all ordered to shut their doors and stop accepting customers.
According to NRK the only known violations of the ban on operating such businesses have so far been in Oslo.
On March 25, Norway's justice minister Monica Mæland acknowledged that some people would increasingly start to feel that they needed a haircut.
“It's not fun to say it, but I still have to do it: You must not do it,” she warned. “It can help spread infection, and so we must try to avoid it by all means.”
In Denmark, Søren Bostrøm, the Director-General of the Danish Health Authority, last weekend cut his own hair with electric clippers, posted the result on Twitter, and sent money to his hairdressers, asking others to follow his example.