Recently, researchers have become increasingly interested in the potential of video games to promote real-life prosocial behavior. It has been argued that in-game prosocial acts may transfer to players’ real-life behavior. But so far little is known about how video games affect players’ in-game as well as future real-life prosocial decisions. To address this research gap, we carried out two experiments. Both studies investigated whether voluntarily choosing to help a game character in the same first-person shooter game affected an ensuing real-life prosocial decision (i.e., donation to a charity). The results of the first study (N = 270) indicate that voluntarily deciding to help in-game subsequently led to increased donating behavior. In study 2 (N = 185) we further analyzed the potential moderating effects of game rewards and players’ reasoning for in-game helping. The results of both studies indicate that voluntarily deciding to help in a video game subsequently led to increased donating behavior. Further, results of Study 2 revealed that the absence of a reward for helping in-game affected players’ reasoning for helping and positively influenced prosocial self-concept and donation.