We study the effects of experimental manipulation of decision mode (rational“brain” vs. affective “heart”) and individualdifference in processing styles (intuition vs. deliberation) on prosocialbehavior. In a survey experiment with a diverse sample of the Swedish population(n = 1,828), we elicited the individuals’ processingstyle and we experimentally manipulated reliance on affect or reason, regardlessof subjects’ preferred mode. Prosocial behavior was measured across aseries of commonly used and incentivized games (prisoner’s dilemma game,public goods game, trust game, dictator game). Our results show that prosocialbehavior increased for the affective (“heart”) decision mode.Further, individual differences in processing style did not predict prosocialbehavior and did not interact with the experimental manipulation.