With a diary study, we tested the positive effect of prosociality on life satisfaction. Fifty-six Spanish undergraduate students (45 females; Mage = 21.08 years) rated their life satisfaction, prosociality, self-esteem, and physical appearance for 5 consecutive days. Multilevel results indicated that within-individual positive deviations in prosociality (i.e., behaving more prosocial than usual) were uniquely and significantly associated with higher life satisfaction on that specific day. Students’ self-esteem, physical appearance, and positive daily events were also predictive of life satisfaction. Exploratory analyses revealed that the positive effect of prosociality on life satisfaction was significant only for those students with low or...