The 25-year-old was arrested at an address in Newham shortly before 5am on Saturday, 12 December. He remains in custody.
Police were called at approximately 18:50hrs on Friday, 11 December to reports of a person stabbed in Woodman Street, North Woolwich.
Officers and London Ambulance Service attended and found a 15-year-old male with a stab wound. Despite the efforts of the emergency services, he was pronounced dead at the scene.
His next of kin have been informed.
Detective Superintendent Paul Whiteman, Head of CID for the North East BCU, said: “I am shocked at this tragic loss of a young life. An arrest has been made but the investigation is still in its early stages. I would appeal to any members of the local community to come forward with any information which might help bring those responsible to justice.
“Local officers will step up patrols in the area in the coming days to reassure the public and continue to target violent crime.”
The investigation is being led by the Met’s Specialist Crime Command (Homicide). Anyone with information is urged to call the incident room on 0208 345 3715.
Alternatively, they can contact the independent charity Crimestoppers, anonymously, on 0800 555 111.