Ambivalence in the decision-making process for living liver donors has the potential to result in their experiencing a negative mental status. To promote donor candidates' well-being, it is important to study the factors related to ambivalence. Thus, the aim of this study was to explore the ambivalence of living liver donor candidates and to investigate the effect of social support and donation-related concerns on their ambivalence. A cross-sectional design was used. In total, 100 living liver donor candidates who underwent a preoperative evaluation between April and October 2009 were recruited for the study. Participants completed a self-administered questionnaire that contained items related to ambivalence, donation-related concerns, and social support. The mean score for ambivalence was 3.14 (standard deviation 5 1.8), and the median was 3. Only 7% of the study sample reported no ambivalence during the assessment stage. Ambivalence was positively correlated with donation-related concerns (physical concerns, r 5 0.39; psychosocial concerns, r 5 0.43; financial concerns, r 5 0.29) and negatively correlated with social support (r 5 20.16 to 20.33). Those with psychosocial concerns had significantly worse ambivalence (b 5 0.29, P 5 0.03), but social support mitigated ambivalence (b 5 20.34, P 5 0.01). When intimacy and social support were included in the model, the effect of psychosocial concerns on ambivalence became nonsignificant (b 5 0.24, P 5 0.08). Ambivalence is common among living liver donor candidates, but instrumental social support can mediate the negative effect of donation-related concerns. Recommendations include providing appropriate social support to minimize donation-related concerns and, thus, to reduce the ambivalence of living liver candidates. Liver Transpl 20: 1365-1371, 2014. V C 2014 AASLD. Received March 19, 2014 accepted July 6, 2014. Living donor liver transplantation (LDLT) was developed to respond to the high demand for organs and the shortage of deceased organ donations.1,2 A remarkable increase in adult LDLT has been observed; currently, these donors account for approximately 10% of all liver transplants in the United States. According to the literature, the percentage of LDLT, compared with those that used organs from the deceased, is 99.2% in Japan, 65.8% in Korea, and 36.5% in Taiwan.