Meta-analytical findings suggested a positive link between trait mindfulness and prosociality. However, most correlational studies on mindfulness and prosociality have relied on self-report measures. The present work aimed to address this serious limitation by investigating actual prosocial behavior. We further focused on mindfulness as a multi-dimensional personality trait to disentangle effects of different mindfulness aspects. In addition, we tested whether the relation between trait mindfulness and prosocial behavior emerges under a theoretical meaningful experimental boundary condition (i.e., feelings of guilt). In two studies (using four different samples; N = 1240), we did not find support for a positive link between trait mindfulness and (a) charitable donation and (b) behavior in an incentivized economic game, respectively. Evidence for manipulated guilt-level as a moderator was inconclusive. Taken together, the findings point to a more complex role of trait mindfulness for prosocial behavior. Limitations and ideas for further research are discussed.