Ambivalence refers to the experience of having both positive and negative thoughts and feelings at the same time about the same object, person, or issue. Although ambivalence research has focused extensively on negative consequences, recently, scholars turned their lens to the positive effects of ambivalence, demonstrating beneficial effects on judgements and decision-making processes. So far, this work has focused on state ambivalence, which is ambivalence as a direct response to a specific stimulus. However, there are substantial individual differences in ambivalence: Some people are just more ambivalent than others. Taking a first step in understanding how these individual differences relate to judgement and decision-making, we examine the relationship between trait ambivalence and cognitive bias in social judgements tasks. Specifically, we look at two of the most pervasive and consequential attribution biases in person perception: correspondence bias and self-serving bias. We find a negative relationship between trait ambivalence and correspondence bias. The higher individuals are in trait ambivalence, the smaller their bias towards attributing behaviour to a person’s disposition (Study 1A and B). We find the same for self-serving bias (Study 2A and B). In sum, we show that trait ambivalence is negatively related to cognitive bias in person perception.