The implications of prosocial behaviour on public service motivation are found. The link between prosocial behaviour and public service motivation from a sense of wanting to help others. In practice, civil servants are often encouraged to help the community. The meeting point between public service motivation and prosocial behaviour is with the choice to become a volunteer. Civil servants who have a robust public service motivation will be involved in voluntary activities. This study aims to examine the effect of volunteerism on the motivation of public services on civil servants in Yogyakarta special government. The method used in this research is quantitative research methods. Questionnaires are distributed at special local government offices in Yogyakarta that provide basic services. The number of respondents who answered the survey was 321 people. Data processing using SEM PLS and data analysis using quantitative descriptive. The results of this study are prosocial behaviour and the value of altruism through voluntarism activity significantly influence the motivation of public services. But directly, prosocial and altruism do not affect public service motivation.