This study examined relationships among personality traits, ego development, and volunteering among retired seniors who were current, former, and new volunteers. Volunteer history, but not extensiveness of volunteer experience, was associated with higher ego development. Current volunteers had higher levels of ego development than former and new volunteers, and former volunteers had higher levels than new volunteers. Openness to experience and ego development were positively associated. Results of multiple-regression analyses indicated that openness and volunteering history and extensiveness positively predicted ego development. This study supported the hypothesis that ego development is related to volunteering and suggests that participation in volunteer work promotes ego development.