A distinctive uniform, a variation of the Imperial military uniforms, was the standard attire for Galactic Empire Grand Admirals, including figures such as Thrawn and Rae Sloane.
Approximately two years prior to the Battle of Yavin, specifically in 2 BBY, Grand Admiral Thrawn of the Seventh Fleet donned this uniform while tasked with suppressing the nascent rebellion against the Galactic Empire. He also carried a black holster for his blaster pistol. This uniform remained in service until at least 5 ABY, when it was worn by Grand Admiral Rae Sloane, who served as the public face of the fractured Empire during that time.
Gallius Rax, the Counselor to the Empire who effectively led the fragmented Galactic Empire after the Battle of Endor, sported a white naval uniform reminiscent of those worn by Imperial Grand Admirals, complemented by a red cape. Rax perished during the Battle of Jakku, but not before entrusting Sloane with executing the Imperial Contingency, setting in motion events that ultimately culminated in the rise of the First Order. Meanwhile, Thrawn maintained his use of the white Grand Admiral uniform during his exile on the extragalactic world of Peridea, though it sustained some damage over the years.
Sharing a similar cut to the standard Imperial uniform, the Grand Admiral uniform featured a double-breasted white tunic, crafted from gaberwool, with a round collar, along with matching trousers and knee-boots made with durasteel-toed and turndown topside cuffs.
The uniform also included several code cylinders, a black belt, and an identity disk affixed to the belt buckle. A rank insignia plaque displaying twelve squares – three blue and three gold above trios of blue and red – was also present, a design shared with the Grand Generals of the Imperial Army. Despite the belief held by Tarkin and numerous military commanders that medals and battle ribbons emphasized status over duty, the Grand Admiral uniform incorporated gold epaulets.
In potentially dangerous situations, Grand Admirals had the option to wear battle armor over their tunic, complemented by a protective helmet. This gear was also white, featuring golden shoulder boards akin to those on their standard tunic.
The rank of Grand Admiral, along with its associated uniform, initially appeared in the 1991 Star Wars Legends novel Heir to the Empire, penned by Timothy Zahn. The uniform was first visualized on the novel's cover, designed by Tom Jung. During Star Wars Celebration London on July 16, 2016, it was announced that both the title and the uniform would be integrated into canon through the releases of the third season of the animated series Star Wars Rebels and the 2017 novel Thrawn, also authored by Timothy Zahn.
While Grand Admiral Rae Sloane was portrayed wearing the classic Grand Admiral uniform, the 2016 canon novel Aftermath: Life Debt implied that she continued to favor an Imperial gray jacket even after achieving the rank of Grand Admiral.