Previous research on political orientations, which can be understood as one's left- versus right-wing attitude, has shown that some personality factors yield explanatory power. In the current work, we consider the role of altruism - a personality construct which does not exclusively map onto one of the broad personality dimensions typically studied. Altruism was predicted to relate to left-wing attitudes due to an overlap regarding concerns for social equality, and a discrepancy between well-known attributes of right-wingers and altruistic individuals, respectively. Moreover, altruism was expected to explain unique variance in political orientation beyond the 'Big Six' broad dimensions as it relates to aspects not covered by the latter. Both hypotheses were tested in a web-based questionnaire study (N = 137). Besides replicating findings of previous research, results corroborated a strong positive association between altruism and left-wing attitudes, and altruism was found to account for substantial variance in political orientation after controlling for the HEXACO factors of personality. We conclude that altruism is an important construct which deserves attention whenever political attitudes or other topics relating to social equality are at stake.