Cross-cultural ethical conflicts are common. However, little is known about how and to what extent acculturation changes attitudes toward end-of-life care and advance care planning. We compared attitudes toward end-of-life care among Japanese Americans and Japanese in Japan. Self-administered questionnaire in English and Japanese. Community-based samples of Japanese Americans in Los Angeles and Japanese in Nagoya, Japan: 539 English-speaking Japanese Americans (EJA), 340 Japanese-speaking Japanese Americans (JJA), and 304 Japanese living in Japan (JJ). Few subjects (6% to 11%) had discussed end-of-life issues with physicians, while many (EJA, 40%; JJA, 55%; JJ, 54%) desired to do so. Most preferred group surrogate decision making (EJA, 75%; JJA, 57%; JJ, 69%). After adjustment for demographics and health status, desire for informing the patient of a terminal prognosis using words increased significantly with acculturation (EJA, odds ratio [OR] 8.85; 95% confidence interval, [95% CI] 5.4 to 14.3; JJA, OR 2.8; 95% CI 1.8 to 4.4; JJ, OR 1.0). EJA had more-positive attitudes toward forgoing care, advance care planning, and autonomous decision making. Preference for disclosure, willingness to forgo care, and views of advance care planning shift toward western values as Japanese Americans acculturate. However, the desire for group decision making is preserved. Recognition of the variability and acculturation gradient of end-of-life attitudes among Japanese Americans may facilitate decision making and minimize conflicts. Group decision making should be an option for Japanese Americans.