Abstract Background Frailty status has been sparsely studied in some groups including Native Hawaiians and Asian Americans. Methods We developed a questionnaire-based deficit accumulation frailty index (FI) in the Multiethnic Cohort (MEC) and examined frailty status (robust, FI 0 to <0.2, prefrail, FI 0.2 to <0.35, and frail FI ≥ 0.35) among 29 026 men and 40 756 women. Results After adjustment for age, demographic, lifestyle factors, and chronic conditions, relative to White men, odds of being frail was significantly higher (34%–54%) among African American, Native Hawaiian, and other Asian American men, whereas odds was significantly lower (36%) in Japanese American men and did not differ in Latino men. However, among men who had high school or less, none of the groups displayed significantly higher odds of prefrail or frail compared with White men. Relative to White women, odds of being frail were significantly higher (14%–33%) in African American and Latino women, did not differ for other Asian American women and lower (14%–36%) in Native Hawaiian and Japanese American women. These racial and ethnic differences in women were observed irrespective of education. Risk of all-cause mortality was higher in prefrail and frail men than robust men (adjusted hazard ratio [HR] = 1.69, 1.59–1.81; HR = 3.27, 3.03–3.53); results were similar in women. All-cause mortality was significantly positively associated with frailty status and frailty score across all sex, race, and ethnic groups, Conclusions Frailty status differed significantly by race and ethnicity and was consistently associated with all-cause mortality. The FI may be a useful tool for aging studies in this multiethnic population.