Rosemary N. DeCaires has extensive experience volunteering and holding leadership positions in community organizations. She has volunteered at Parkdale Community Legal Services since 1991 and Elections Ontario since 2003. She has also held executive roles at Hart House University of Toronto, organized fundraising for the Ontario Labour Relations Board, served as a student liaison for the Union of Political Science Students, and was student representative and president of the student council at St. Joseph College School.