In the ever-evolving landscape of health systems, citizen advocacy stands as a tool for influencing policy aiming to strengthen health systems. This dissertation delves into the multifaceted nature of health policy advocacy and how citizen advocates can leverage research evidence in addition to the commonly used emotional messaging to influence policy. The first study is a critical interpretive synthesis (CIS), creating a theoretical framework that helps us understand the roles of citizen health policy advocates and their relation to research evidence. The second study is a multiple-case study that examines the approaches taken by citizen-serving NGOs in their advocacy training and whether and how research evidence is incorporated into the training. The third study is a qualitative descriptive study that explores citizens' experiences participating in these training modules and their perceptions of factors affecting the incorporation of research evidence in the training. In Chapter 2, we included 32 publications in the CIS, and four thematic groups were identified, including the roles of citizen health policy advocates, how research evidence could support them and the facilitators and barriers to their use of research evidence. In Chapter 3, we conducted a documentary review of 27 documents and interviewed 16 staff and board members of three organizations that provide advocacy training to citizen advocates. In Chapter 3, we interviewed 14 citizens who participated in the training of the three organizations. v The first study outlined how citizens could use research evidence and its importance to their advocacy roles, while the last two studies provide an understanding of how citizen-serving organizations offer training to citizen advocates and whether, how, and under what conditions they include research evidence in training. / Thesis / Doctor of Philosophy (PhD) / Advocacy is an effective way to influence policies in democratic societies. One of those areas that are influenced by policy advocacy is health systems. Citizens who advocate for improving their health systems often rely on personal emotional messages rather than peer-reviewed research evidence. This dissertation tries to understand why this is the case and how research evidence can support those citizens. We also explore the factors that encourage or hinder citizens from using research evidence in health policy advocacy. We then examine three citizen-serving organizations that support citizens with advocacy training and explore how they support the trainees to use research evidence in advocacy. We also examine the experiences of citizens who participated in those training sessions and how they perceive the utility of research evidence in their advocacy to strengthen their health systems.