Approximately one in 10 Australian individuals report bisexual attraction, and this group has repeatedly been found to experience high rates of poor mental health. Despite this finding, our understanding of who is most at risk within this group remains limited. The current article presents findings of an online survey conducted in Australia with one of the largest samples of bisexual adults to date (N = 2,651). Chi-square and regression analyses identified significant associations between the three dimensions of bisexuality (i.e., identity, behavior, and attraction) and mental health. Participants who reported identifying as bisexual were found to be especially vulnerable to poor mental health compared to those who reported bisexual attraction and/or sexual experiences without a bisexual identity. These findings provide a significant contribution to the lacking literature on the complexities of bisexual orientation and mental health. [Journal of Psychosocial Nursing and Mental Health Services, 58(3), 28-37.].