The victims, both in their 50s, were shot in the head after two gunmen walked into the Beckton Arms in Canning Town, on Sunday afternoon.
The victims, who were apparently targeted specifically, were named as Tommy Hole, 57, and Joey Evans, 55, - known locally as The Crow - who both lived in the area.
The men were known to the police and Mr Evans was said to owe a considerable amount of money.
Scotland Yard are investigating whether the double murder was a contract killing or possible revenge attack. East End criminals and several violent gangs are known to operate from the area.
A 31-year-old man was arrested early yesterday in east London and was being held at a police station for questioning.
At the time of the attack about 20 customers had gathered in the pub to watch a football match on television.The two killers entered the pub at about 3.20pm armed with handguns. One witness said: "I heard about six shots. I didn't look, I just pulled myself and my wife to the floor."
An air ambulance was called but paramedics pronounced the victims dead at the scene, about 20 minutes after the attack.Reuse content