This systematic review aims to address four key questions regarding patient engagement in healthcare research: how to identify patient representatives, how to engage them in research design and conduct, what are the observed benefits, and what are the harms and barriers. The review includes 142 studies published in English, covering various engagement methods and outcomes. Patient engagement was found to be feasible in most settings, particularly at the initial stages of research (agenda setting and protocol development). Common engagement methods include focus groups, interviews, surveys, and serving on study boards. Benefits of patient engagement include increased study enrollment rates, improved funding, and better alignment with patient concerns. Challenges include logistical issues, time constraints, and concerns about tokenistic engagement. The review highlights the need for further research to identify best practices and address the potential for tokenistic engagement.This systematic review aims to address four key questions regarding patient engagement in healthcare research: how to identify patient representatives, how to engage them in research design and conduct, what are the observed benefits, and what are the harms and barriers. The review includes 142 studies published in English, covering various engagement methods and outcomes. Patient engagement was found to be feasible in most settings, particularly at the initial stages of research (agenda setting and protocol development). Common engagement methods include focus groups, interviews, surveys, and serving on study boards. Benefits of patient engagement include increased study enrollment rates, improved funding, and better alignment with patient concerns. Challenges include logistical issues, time constraints, and concerns about tokenistic engagement. The review highlights the need for further research to identify best practices and address the potential for tokenistic engagement.