The prospect of a reward can enhance cognitive performance. For younger men financial gains, and for older adults and women prosocial rewards, seem particularly motivating. We therefore investigated whether adding a prosocial component to a financial reward enhanced cognitive performance and, if so, whether this depended on age or sex. We randomly assigned 571 participants to one of three reward types (financial reward, prosocial reward, or a combination of both) in a monetary incentive delay task. We used linear effects modelling to examine effects of age, sex, or reward type on trial accuracy, response time, and total performance. The prospect of a combined financial and prosocial reward increased performance in all participants with the increase of response speed particularly pronounced in younger adults. Only in men, a sole financial reward increased performance. Our study highlights the importance of choosing rewards wisely when designing studies that examine their influence on cognitive performance.