Officers first raced to Courtland Avenue at 8.11pm on Thursday following reports of a fight in progress but were unable to find any victims.
The London Ambulance Service then alerted police about a man, aged in his 20s, who had been stabbed at Barnet Bypass, near Scratchwood Park.
A Met Police spokesman said: "The man was treated at the scene by paramedics before being taken to hospital.
"After a search of a car found at the scene, a man, in his 30s, was found inside a vehicle with stab wounds.
"Despite the efforts of emergency services, he was declared dead a short time later.
"Enquiries are ongoing to notify his next of kin. A post-mortem examination will take place in due course."
A crime scene has since been put in place and an investigation into the stabbing has been launched.
It comes after officers were called to a separate stabbing earlier that day in Bromley Road in Walthamstow at 7.16pm following reports of the two men suffering from stab injuries, according to police.
One man, believed to be in his 20s, was pronounced dead at the scene and the other, also thought to be in his 20s, was taken to hospital. His condition is not thought to be life-threatening.
An arrest has been made in connection with the Walthamstow stabbing and inquiries continue.
This is a breaking news story and is constantly being updated.
Please refresh the page regularly to get the latest updates.
Reporters working on dailystar.co.uk will be working to source the latest information, reaction, pictures and video related to this story.
Or download the Daily Star app for flash alerts on the biggest stories of the day.
Why not also subscribe to receive our regular Daily Star news bulletins? You can do this on this page by simply entering your email address above and hitting 'subscribe'.