Previous reviews have indicated that immigration from South Asian to Western countries leads to unhealthy changes in diet; however, these reviews have been limited by the methods used in some included studies. This critical narrative review summarizes findings from original research articles that performed appropriate statistical analyses on diet data obtained using culturally appropriate diet assessment measures. All studies quantitatively compared the diets of South Asian immigrants with those of residents of Western or South Asian countries or with those of South Asian immigrants who had varying periods of time since immigration. Most studies examined total energy and nutrient intake among adults. Total energy intake tended to decrease with increasing duration of residence and immigrant generation, and immigrants consumed less protein and monounsaturated fat compared with Westerners. However, findings for intakes of carbohydrate, total fat, saturated fat, polyunsaturated fat, and micronutrients were mixed. Studies that examine food group intake and include South Asians living in South Asia as a comparison population are needed.