The purpose of this study was to analyze those factors affecting volunteering in sport associations of universities in Tehran. The research was a descriptive, survey and field study and was categorized as an applied research based on its aim as well. In order to collect the data, a questionnaire (Andam, 2007) was used and distributed among target population which consisted of all boys and girls who were a member of these sport associations. The questionnaire consisted of seven motivational variables: career, material, enhancement, purposive, social, protective and commitment. For data analysis, descriptive and inferential statistics were applied. Results showed that the variables were ranked as follows: material, social, career, enhancement, protective, commitment and purposive. Furthermore, the analysis of the difference between boys and girls in all variables showed no significant difference in social, career, enhancement, protective and commitment variables (P>0.01) and on the other hand, there was a significant difference in material and purposive variables between boys and girls (p<0.01). Managers in the universities and their physical education offices must prioritize these variables and (especially material and social variables) and pay attention to their roles in planning and policy making so that they can achieve volunteering advantages.