Memory for future actions, or "prospective memory" (PM), often involves remembering to do things "for others". The present article explores the motivational mechanisms underlying memory for pro-social intentions through the manipulation of the social relevance of goals and presence of material rewards during an activity-based PM task. Results revealed that memory for the intention was better under pro-social than under standard conditions. However, when a material reward was introduced under pro-social conditions, it had the detrimental effect of reducing prospective remembering. Ongoing task performance was faster under pro-social than under No PM and standard PM conditions and it was unrelated to PM performance. In addition, the outcome of the ratings of two independent groups of participants confirmed that people are not aware of the potential conflict between pro-social and self-gain motives. Taken together, these new findings extend current PM theories by suggesting a prominent role of latent motivational mechanisms in guiding memory for pro-social intentions. (Contains 1 figure and 2 tables.)