Because trust is essential in the development and maintenance of well‐functioning relationships, groups, and societies, scholars across numerous scientific disciplines have sought to determine what causes people to trust others. One important predictor of trust is social power. However, the relationship between social power and trust remains inconclusive. On the one hand, social power research suggests that powerful individuals trust others less because they are concerned about being exploited for their resources. On the other hand, sociological research suggests that people who lack resources tend to be more distrustful. The present research suggests that both may be true. Based on theories of social exchange suggesting that self‐interest tends to be more salient when resources are distributed unequally (vs. equally) and recent research showing that high‐ and low‐power individuals sometimes share a similar psychology, we propose that interpersonal trust will be lower in unequal‐power (vs. equal‐power) relationships and that this effect is explained by lower perceived goal similarity. Seven experiments (including four pre‐registered; N=4,247) demonstrate that both high‐ and low‐power individuals in unequal‐power relationships trust each other less compared to individuals in equal‐power relationships, and that this is due to lower perceived goal similarity. This effect occurs for affect‐based (but not cognition‐based) trust and for relational (but not psychological) power. We also provide a theoretically motivated intervention (introducing intergroup competition) that facilitates trust even in hierarchical environments. Overall, this research suggests that power (in)equality may be a more proximate predictor of interpersonal trust than the amount of power one has.