Many people hold cynical views of humanity, which are associated with negative outcomes such as lower trust and cooperation. Can cynical beliefs be altered? While some long-term strategies seem effective, new research shows that anticipating changes in others’ behaviour may be influential in altering people’s perceptions/actions. Capitalizing on this insight, we introduce the idea of prosocial fantasies: instances where a person daydreams, fantasizes or imagines themselves helping others in the future. Studies 1a-b explored the prevalence, frequency and content of undergraduates' (pre-registered; N=488) and ex-offenders' (N=25) prosocial fantasies, and Study 2 (pre-registered; N=637) examined if presenting prosocial fantasy rates to a nationally representative panel of Americans can lower cynicism. Results indicated that a majority of people have prosocial fantasies, involving a range of targets from family to distant others, however, learning about prosocial fantasy rates does not reduce cynicism. Findings suggest that cynicism may not be altered by shorter interventions.