At 5.46am on October 27, Metropolitan Police officers attended Taunton Way in Stanmore following reports of an assault.
The London Ambulance Service received reports of a stabbing at 4.24am.
The response included paramedics travelling in fast-response cars, an ambulance crew and an incident response officer.
A trauma team from London’s Air Ambulance also reached the area by car.
The service treated a patient at the scene before taking him to a major trauma centre as a priority.
According to the Metropolitan Police, the victim, a man aged 45, was taken to hospital with stab wounds.
His injuries were not believed to be life-threatening or life-changing.
Another patient, a woman in her 30s, went to hospital after an assault.
Her injuries were likewise not believed to be life-threatening or life-changing.
Police detained a 45-year-old man on suspicion of grievous bodily harm, and he remains in custody.
Anyone holding information that could assist the investigation was asked to contact police on 101 and quote CAD 766/27Oct.