The aim of this study was to investigate why people with a first episode of psychosis choose or decline to participate in mental health research, using a qualitative study design. Participants were recruited via referrals from the Genetics and Psychosis (GAP) study. A total of 26 individuals with a first-episode of psychosis (nine of whom declined participation in the GAP study and 17 who participated) were individually interviewed and asked about their attitudes towards mental health research participation. Thematic analysis of interview transcripts was used to determine dominant themes and sub-themes on what constituted barriers and facilitators to participation. Reasons for research participation identified included a desire to help others, curiosity, and positive experiences with clinicians. Decisions to participate or not were also influenced by practical issues, including the timing of the approach, researchers' communication skills and whether individuals had concerns that it may be potentially harmful to their health. Other barriers to participation included patients' conceptualizations of mental health problems and the influence of other inpatients. Information on barriers and facilitators to recruitment in mental health research could inform recruitment strategies, thereby maximizing recruitment rates and minimizing the risk of selection biases.