Altruism in the volunteer community is often associated with volunteers taking action in the volunteer community. Altruism is giving voluntary assistance to others without expecting anything in return. This study describes the factors influencing altruism and motivation for volunteer altruism, as well as the impact of altruism in building social solidarity in Siaga Peduli Magelang. This study is qualitative with a case study approach. The informants of this study are Siaga Peduli Magelang administrators who have been involved in volunteer activities for at least one year. The results of the study indicate that there are factors influencing altruism in this community, namely empathy, self-satisfaction, and belief in world justice, that goodness will be rewarded in kind by God. The motivation for volunteer altruism in the Siaga Peduli Magelang community is closely related to the empathy that drives the prosocial behavior of the informants. The motivation for prosocial behavior in the Siaga Peduli Magelang community is divided into pleasure and pressure dimensions. There is an impact of altruism in building social solidarity in Siaga Peduli Magelang. Altruism in volunteers is deeply embedded so that it increases social solidarity to continue to contribute to the field of volunteerism.