Although it is well known that volunteering is associated with happiness, little has been examined regarding associations between volunteering and happiness according to the type of volunteering and the volunteer’s economic standing. The data used in this study were drawn from the 2012 Korean General Social Survey, a nationally representative survey. Multiple regression techniques were used to examine associations between three volunteering types (for a residential community, with an educational purpose, or for socially vulnerable groups) and happiness, and if and how their associations vary by the volunteers’ household income. The findings showed that volunteer activities for a residential community and for socially vulnerable groups were positively associated with happiness after controlling for sociodemographic factors, but they were not significant after controlling for personality traits, generalized trust, and self-rated health. An examination of the interactions between each volunteering type and household income revealed that the association between volunteering for socially vulnerable groups and happiness varied by income. Volunteering for socially vulnerable groups was more positively associated with happiness as income level increased. However, it turned out to be negatively associated with happiness for low-income volunteers. The findings suggest that the effects of volunteering on happiness are complicated by the characteristics of volunteering and the social conditions of the volunteers.