Sharif Zaiden, 18, was shot on the dancefloor in a private function room at Egg in King's Cross in the early hours of Saturday 12th August.
A 27-year-old man was arrested Thursday 17th August and is being questioned by police.
Sharif Zaiden was shot four times on the dancefloor at Egg
Egg nightclub expressed their "sincere condolences" to Sharif Zaiden's family in a statement, but also reported that the shooting had occurred at a one-off private party that was held away from the main club.
The statement said: "We are all deeply shocked and horrified that such an incident should take place on the premises."
The club said it was cooperating fully with the police and other authorities investigating the shooting, but insisted the private function room had its own entrance and security.
About 200 people were celebrating the club's first anniversary when the attack happened at around 3am.
Copyright Thrust Publishing Ltd. Permission to use quotations from this article is granted subject to appropriate credit being given to www.djmag.com as the source.