The Global Defense Initiative has employed several types of uniforms in its history, all emphasizing functionality over aesthetics.
First Tiberium War
GDI adopted the United States Army Class A Green Service Uniform with minor modifications. The uniform features a jacket with four buttons, worn with an off-white dress shirt and black tie. Officers wear a pair of the GDI insignia on their lapels.
Proficiency badges, such as the marksman's badge, are worn on the upper left pocket flap. Above this are the ribbons for medals and commendations which have been earned for various actions, duties and training. Above the ribbons are qualification badges, such as the paratrooper badges and Combat Action Badge. A nametag is worn on the upper right pocket flap.
Desert Battle Dress Uniform
Soldiers in regular combat duty used an American Desert Battle Dress Uniform with the six-color "chocolate" chip camouflage pattern, along with a PASGT vest and helmet.
Second Tiberium War
GDI continued to employ the Class A Green Service Uniform. Interestingly, it seems General Solomon retained his "U.S." lapel pins, rather than replace them with the standard label pins with GDI emblem (Like the ones that general Paul Cortez wore). Enlisted servicemen service uniform consist of a khaki shirt, pants and tie, with a pair of pins bearing the GDI insignia on the collars of the shirt.
- Main article: GDI combat uniform
Soldiers in active combat duty were issued one of two types of single-piece combat uniforms.
Type 1 combat uniform was plain colour, featuring two breast pockets with angled openings, with the cloth nametag (black on white background) worn over the left one. The GDI insignia (cloth also) is worn on the upper left sleeve. Rank insignia is worn on the right sleeve.
Type 2 combat uniform came in three-colour desert camouflage, two regular breast pockets, with the GDI insignia placed on the right pocket and the nametag above the left pocket flap. Rank insignia was worn on the left sleeve.
Some GDI officers wore non-regulation clothes along with the uniform, eg. a leather flight jacket in the case of Michael McNeil.
In combat, it was usually worn with a helmet, armoured breastplate and heavy gloves. Together with the uniform, they gave decent protection from environmental hazards and gunfire, while the helmet itself featured a full heads-up display giving the user a high level of battlefield awareness.
Third Tiberium War
By 2047, GDI became the de-facto world government and redesigned their uniforms, adopting a plain colour simple pattern uniform, made up of a long sleeve plain colour shirt with two breast pockets, plain colour blue trousers with cargo pockets (plain colour skirt for ladies) and a patrol cap. The only allowed insignia are a single GDI patch in subdued (black and grey) colours worn on the right sleeve at shoulder height, metal name tag above the left breast pocket and a single metal GDI insignia pin worn in the left lapel.
High ranking personnel, such as General Jack Granger may also wear bulletproof vests, with their rank displayed on the left side of the vest and the metal name tag on the right.
By the time of the Ascension Conflict the GDI uniforms were redesigned to that of its predecessors from 1995. In addition, several members wore the U.S. Army Universal Camouflage Pattern (UCP).