This article reports the development of an acculturation scale for Southeast Asian immigrants. From factor analyses of responses on 13 items obtained from samples of three different Southeast Asian ethnic groups, i.e., Cambodians, Laotians, and Vietnamese, two subscales were derived: (1) proficiency in languages (land of origin versus English), and (2) language, social and food (LSF) preferences. Inter-item reliability of the scales was demonstrated for each of the three ethnic groups, with Cronbach alpha coefficients of 0.76 or above. Construct validity was also established within each of the three ethnic groups by demonstrating expected associations of the subscales with current age, years in the USA, total years of education, percentage of lifetime in the USA, and age on entering the USA. Multivariate analyses within each of the ethnic groups revealed that, once controlling for years of education, percentage of lifetime in the USA, and type of health care coverage, although not significant for the Cambodians (P = 0.08) males tended to show higher scores for the proficiency in language subscale in comparison to females. Similar multivariate analyses for the LSF preference subscale showed that although slightly higher for the males, the differences between the genders was not significant for the Cambodians (P = 0.78); both the Laotian (P = 0.23) and Vietnamese (P = 0.01) females showed higher scores in comparison to males although only just reaching significance for the Vietnamese.