Police were called to Wealdstone High Street around 7pm on Tuesday, November 30 following reports of a stabbing. Metropolitan Police officers and London Ambulance Service paramedics attended the scene and found two boys, aged 14 and 16, with stab wounds.
The teenagers were taken to a hospital in West London where their injuries were assessed as non-life-threatening.
A short time later, a third victim was found outside Harrow and Wealdstone Station suffering from life-threatening stab wounds.
The 22-year-old man was rushed to a west London hospital for emergency treatment, where he remains in a stable condition.
Following the attacks, police taped off Wealdstone High St and closed the station to investigate.
Detectives warned members of the public that they would see a significant police presence in the area following the attacks.
Images shared by Harrow Online showed numerous police vehicles attending the scene while the cordon around the crime scenes was in place.
A statement from the Metropolitan Police added that a Section 60 order, which gives police additional stop and search and arrest powers, had been authorised until 8am on Wednesday morning.
A Metropolitan Police spokesperson confirmed to Express.co.uk that two arrests had been made following the attack.
The force is urging anyone who witnessed the incident to call 101 with the reference 6046/30NOV.
Information can also be provided to Crimestoppers, anonymously, on 0800 555 111.