Munashe Charles Kutyauripo, 16, known as Charlie, was attacked at Ashton Playing Fields following his friend's party at Woodford social club.
Police said the boys were arrested at separate addresses and were in custody.
Detectives are continuing to search for 16-year-old Aaron Alexander Tavares-Gaiete.
Detective Chief Inspector Mark Lawson said Charlie's family had been left "devastated" by his death, and "wanted and deserved answers" about what happened.
His family said in a statement: "We hope that if anybody knows anything, they should come forward and help find whoever did this because to the world he was just a 16-year-old boy, but to us, that was our son taken."
A post-mortem examination found he died from a stab wound to the chest.
Two 17-year-olds have been arrested on suspicion of murdering a teenage boy who was stabbed after a birthday party in east London.