Voluntary engagement is crucial for committed participation in Citizen Science (CS) projects. So far, the CS literature has argued that psychological ownership (i.e., subjective feelings of owning or possessing an object or entity) facilitates engagement in CS projects and is beneficial for several outcomes, such as attitudes toward CS. We argue that, as ownership is a self-relevant experience, it should influence other self-focused outcomes, such as the self-conscious emotion of pride. Therefore, the research presented here investigated the interrelations between psychological ownership and pride in five two-month long, two-wave longitudinal field studies of a CS project on urban wildlife ecology using cross-lagged panel analyses. We hypothesized that ownership has a positive impact on pride and not vice versa, as pride may take some time to develop and may therefore be particularly relevant at the end of a project. We found that, across all field studies combined, ownership had indeed a positive, time-lagged influence on pride. Thus, when people voluntarily engage in an activity that feels like their own, they also subsequently feel proud, which can motivate further voluntary behavior.