Objective For the proper treatment of first-episode psychosis, assessment of treatment response, remission, relapse, and recovery is important. Therefore, the present study aimed to develop operational definitions of clinical outcomes in first-episode psychosis. Methods A questionnaire was developed by a panel of experts and underwent three revisions. The final survey was presented to 150 psychiatrists who were members of the Korean Society for Schizophrenia Research. Respondents selected factors that they believed were important to consider while defining treatment response, remission, relapse, and recovery using a 6-point Likert scale. Selected factors that constituted each definition were statistically extracted, and operational definitions were developed. Results A total of 91 experts responded to the survey. The extent of reduction in psychopathology, socio-occupational functioning, and duration of each state were the core factors of each definition. Outcomes obtained from discussions and consultations by experts have been summarized and proposed. Conclusion The criteria developed in this survey tended to be somewhat stricter than those used by other studies. The fundamental reason for this is that this survey focused on first-episode psychosis. A better understanding of each definition in first-episode psychosis is necessary to improve effective treatment outcomes.