Police were called at 19:16pm on Thursday, 19 December to an altercation on Bromley Road, E17.
Officers attended along with the London Ambulance Service and found a man, aged in his 20s, suffering stab injuries. Despite the work of emergency services, he was pronounced dead at the scene.
A 29-year-old man was arrested nearby on suspicion of murder and remains in custody.
Detective Chief Inspector Dave Whellams, who is leading the investigation, said: “We are appealing for anyone who was on Bromley Road or nearby Forest Road at around 7.15pm last night to come forward and let us know what they saw.
“We are particularly keen to hear from anyone nearby who may have CCTV of the incident or the events leading up to it.
“All information will be treated in confidence and could make a significant difference to our investigation.”