The 35-year-old was in his vehicle in Cairngorm Crescent, Wishaw, when he became aware of a dark-coloured Citroen car pulling up behind him.
The passenger from the Citroen got out, pulled the victim’s door open and attacked him with a blade before speeding off.
The man made his own way to Wishaw General Hospital, where medical staff say he is in a stable condition.
Police are appealing for information about the incident which happened at about 1am on Sunday in the North Lanarkshire town.
Detective Sergeant John McFall said: “This has been an unprovoked attack and it’s imperative we establish exactly what has happened and why this man has been attacked.
“He has suffered a serious injury to his arm when all he was doing was dropping some friends off after a night out.
“I am appealing to anyone who was in the area around the time of the incident who may have seen or heard anything which could assist our enquiries to contact us.”
Officers have been carrying out door-to-door enquiries in the area and are reviewing CCTV footage.
Anyone with information is asked to call officers at Wishaw CID via 101, quoting incident number 0413 of April 22 or call Crimestoppers on 0800 555 111 where information can be given anonymously.