Sinclair is depicted as being below average height. He has golden blond hair with golden eyes and a fair complexion.

His primary work attire consists of a plain white shirt tucked into a black waist belt and is accompanied by black suspenders, black suit pants, and a long Limbus Company coat. He wears a red necktie and attached to his left suspender strap is his ID. Sinclair has black gloves and wears black oxfords at his feet.