Her commanding physical presence dispelled any sense of impropriety. "Miss Dix was the stateliest woman I ever saw," Ann Wittenmyer wrote, "Her dress was always exceedingly clean and her linen collar and cuffs always immaculate." Dix extended her personal fastidiousness to the standards for nurses at the beginning of the war, writing,

No young ladies should be sent at all, but some who ... are sober, earnest, self-sacrificing, and self-sustained; who can bear the presence of suffering, and exercise entire self-control of speech and manner; who can be calm, gentle, quiet, active, and steadfast in duty.

Their clothing should reflect their mature sensibility: "All nurses are required to be plain looking women, Their dresses must be brown or black, with no bows, no curls, no jewelry, and no hoopskirts."