Police were called to reports of a stabbing in Southall, west London, at just after 9pm on November 24.
A 19-year-old man has been arrested on suspicion of murdering a 16-year-old boy.
le police métropolitaine said the man was arrested on Tuesday and is in custody.
Rishmeet Singh, 16, was found with stab wounds after officers were called to Raleigh Road in Southall west London, at just after 9pm on November 24.
Police were looking into reports of a stabbing following a fight involving a group of people.
Rishmeet, who was from the local area, died at the scene a short time later.
It was the 28th teenage killing in the capital this year, passing the 27 dans 2017.
The Metropolitan Police described the arrest as “a significant development” but called for anyone with information to come forward.
Detective Chief Inspector James Shirley, mener l'enquête, mentionné: “My thoughts continue to be with Rishmeet’s family and friends following this development in our investigation.
“While one man remains in custody, we still need anyone who has any information about the events that led up to Rishmeet’s death to come forward and speak to us.”
The investigation is being led by homicide detectives from the Met’s Specialist Crime Command.