After the 1 Gundam was badly damaged by ex-Fereshte Gundam Meister Fon Spaak's GNY-001F Gundam Astraea Type F, Beside Pain brought it to a secret factory within an orbital elevator that was one of the places Alejandro Corner used to assemble the GNX-603T GN-X. There, he repaired and upgraded the 1 Gundam into the 1.5 Gundam. It is named based on all its abilities being 1.5 times that of the 1 Gundam's. Its aerial combat capabilities are described by Beside Pain to be much higher the Astraea Type F's.
The main distinguishing feature of the 1.5 Gundam is the two new binders on its back, which can be used to enhance the suit's offensive power, defensive power and mobility. The binders are also armed with Binder Rifles and can function as a powerful beam cannon known as Alvaaron Cannon. The 1.5 Gundam retains the armaments of the 1 Gundam, but uses a GN Buster Rifle instead of a GN Beam Rifle.