The men, aged 18 and 19, were detained at Heathrow Airport on Tuesday by police investigating the killing of Omar Abdullah, who died after he was stabbed last Monday along with another man who remains in hospital.
Officers arrested the two teens on suspicion of murder, attempted murder and grievous bodily harm and held them at west London police stations.
Detectives said Abdullah was stabbed at Gayhurst House, a flat block in the Lisson Grove area near Regent’s Park at around 3.20pm on Monday 28 November.
Police and paramedics, including the London Air Ambulance, attended the scene on Mallory Road to find two men with stab injuries.
Abdullah was pronounced dead at the scene while the second man, a 20-year-old whose identity has not been revealed by police, was taken to hospital, where he remained nine days later.
Later on 28 November, a third man, 21, attended hospital with a hand injury believed to have been sustained as part of the earlier incident.
Police continue to look for evidence in the case and have asked the public to come forward with any relevant information.
Detective Chief Inspector Brian Howie of Metropolitan Police, who is leading the investigation, said: “Despite the arrests made, we are still very keen to hear from anyone who has information or footage relating to this horrific incident.
“While police challenge knife crime as a priority, we can’t stop violent behaviour such as this without help from the public – there needs to be a joining of minds where police and the community work together to stamp out the carrying of knives and the violence associated with that.
“If you have information please share what you know. What you tell us, no matter how small, could be a missing piece of the puzzle we are building around Omar’s death. I urge anyone with information about this case to contact us without delay.”
Anyone with information that could assist the investigation is asked to call police on 101 or tweet @MetCC quoting CAD 4334/28Nov. To remain anonymous contact the independent charity Crimestoppers on 0800 555 111.