Construction of the 1,000 tonne steel frame for the temporary venue only started in March.
But the 12,000 seats will soon be installed and the arena will be finished by next April.
Olympic Delivery Authority (ODA) Chairman John Armitt said: “The Basketball Arena is going up rapidly and has been a feature of the East London skyline for some time now.
“Just seven months after work started on the structure, the seats are ready to be fitted.
“As the fourth largest sports venue on the Olympic Park by capacity, it is encouraging that work is continuing at an excellent rate and it is on track to complete next year in time for Test Events.”
The main internal steelwork providing the framework for the building’s services and amenities below is nearly complete, while the installation of scaffolding required to support the seating has now begun.
The seating frame and seats will then be put into place a section at a time so work can start on installing facilities underneath – including lifts, toilet blocks, corridors and VIP access rooms.
It is planned that the first block of seating will be complete by early September to make way for the construction of the first of eight spectator toilet blocks.
The venue, which is as high as the Tate Modern at 35 metres and longer than a football pitch at 115 metres, is wrapped in 20,000sqm of recyclable white PVC membrane that has been stretched over three different variations of arched panels.
During the games the exterior will act as a canvas for an artistic and innovative lighting design.
After the Games the venue will be dismantled by owner Barr with the option of potentially using elements of the arena at other UK and overseas events.
Companies which have won contracts for the Basketball Arena include:
Barr Construction in Glasgow built the structure.
Slick Seating in Redditch is providing the temporary seating.
Base from Bristol provided the membrane cladding for the outside of the Arena.
Envirowrap from Tenterden in Kent is providing the wrapping for the seats.
Sevenoaks-based Volker Fitzpatrick is erecting the steelwork, building the toilet blocks and internal fit-out, including lifts.
McAvoy from Dungannon is building the temporary accommodation.
Fullflow Group Ltd in Sheffield is a sub-contractor to Barr Construction and will be installing the syphonic drainage.