Left to right: Harinder Kumar, Baljinder Singh, and Narinder Singh Lubhaya
The 29-year-old attended a local police station today and has been arrested on suspicion of conspiracy to cause grievous bodily harm.
He remains in police custody.
Investigators are still appealing for witnesses to the attack to come forward.
Narinder Sign Lubhaya, Harinder Kumar and Baljinder Singh all died following the disturbance in Salisbury Road and Elmstead Road on Sunday, 19 January.
The trio were found with stab wounds and all were pronounced dead at the scene.
Detective Chief Inspector Paul Considine, who is leading the investigation, said: “I know that people were present when the attack occurred, I urge them to come forward.
“This is a dreadful incident that has shocked the local community. I need their help to piece together exactly what happened and the events that led up to it.”
Anyone with information is asked to contact investigators on 020 8345 3865 or, to remain anonymous, call Crimestoppers on 0800 555 111.
Two men had previously been arrested; one of them has since been eliminated from police enquiries and is no longer a suspect.
The other, Gurjeet Singh, 29, of South Park Crescent, Ilford, was charged on Tuesday, 21 January with possessing an offensive weapon in a public place.
He has been remanded in custody to appear at Snaresbrook Crown Court on Wednesday, 19 February.
Police say, at this stage, they are not looking to make any further arrests for murder.
Tags: Seven Kings, Redbridge, Ilford
