This thesis explores how meanings of the concept of advocacy are produced by organizational structural features; how the concept of advocacy is constructed and related to young people's experiences by provincial and territorial child and youth advocate offices; how concepts of advocacy come to have significance in the lives of advocates and how they negotiate these concepts in their daily routines; and how children's rights are operationalized in practice in advocate offices. A total of 26 participants are included in the study. Through semi-structured interviews, I engage primarily with provincial and territorial child and youth advocates from across Canada as well as international children's commissioners from Australia, New Zealand, Belgium, Denmark, Norway and Northern Ireland. Two internationally recognized children's rights advocates are also included in the study. Adopting a qualitative methodology, I draw on organizational theory to make meaning of the data. My research reveals that the concept of advocacy is complex. Effective advocacy centres on challenging and changing decision-making processes by partnering with young people to elevate their perspectives and adopting a rights-based approach to working with children and youth. At the provincial and territorial level, it is important for advocates to navigate the historical, cultural and political factors that inform discourses surrounding childhood as these factors impact the way advocacy is carried out. At the organizational level, collaborative relationships with community organizations, government and interdisciplinary advocate teams help to operationalize rights in advocate offices. Findings point to the importance of thinking critically about the concepts of voice, agency and participation in the context of child and youth advocacy institutions. Understandings about children, voice, agency, participation and rights materialize certain groups of children in practice and frequently hinder the viewpoints of young people. Contained within these understandings are processes of exclusion, that may harm some children when considering who gets to have a voice or participate? While the advocates do good things for children, a shift is required in social institutions for children that has a lot to do with a conceptual shift in thinking about these concepts and how advocacy is carried out in 21st century contexts.