Costly third-party interventions have been regarded as hallmarks of moral behavior, because they are unlikely to be motivated by self-interest. This research investigated the cognitive and emotional processes underlying two types of costly third-party interventions by manipulating incidental emotions and attention focus. In Study 1, we investigated the effect of incidental anger on third-party punishment decisions. Study 2 addressed the effect of incidental anger on third-party compensation decisions. In both studies, participants were induced to either an angry or neutral emotion and then had to wait or were distracted before engaging in third-party interventions. In Study 1, angry participants punished highly unequal distributions significantly more than those in the neutral emotion condition. In Study 2, angry participants compensated highly unfair distributions significantly less than those in a neutral emotion. In both studies, the effect of incidental anger was only significant in the wait, not the distraction condition. Study 3 again focused on third-party compensation decisions. Participants were induced to either a self-focused anger or an other-focused anger emotion, and attention focus (wait, distraction) was manipulated experimentally. Those in the other-focused anger condition compensated significantly more than participants in the self-focused anger condition. These results indicate that (self-focused) incidental anger led to antagonistic responses. Incidental anger was only associated with higher third-party compensation when it included a focus on a suffering other. For incidental emotions to bias subsequent decisions requires attentional resources.