Background Core patient characteristic sets (CPCSs) are increasingly developed to identify variables that should be reported to describe the target population of epidemiological studies in the same medical area, while keeping the additional burden on the data collection acceptable. Methods We conduct a systematic review of primary studies and protocols that aim to develop a CPCS, using the PubMed database. We extract information on the study design and the characteristics of the proposed CPCS. The quality of Delphi studies is assessed by a tool proposed in the literature. All results are reported descriptively. Results Among 23 eligible studies, Delphi survey is the most frequently used technique to obtain consensus in CPCS development (69.6%, n = 16). Most studies do not include patients as stakeholders. The final CPCS rarely includes socioeconomic factors (26.1%, n = 6). Besides, 60.9% ( n = 14) and 26.1% ( n = 6) of the studies provide definitions and measurement methods for items in the CPCS, respectively. Conclusion This review identifies considerable variation and suboptimality in many methodological aspects of CPCS studies. To improve these shortcomings, guidance on the conduct and reporting of CPCS studies should be established in the future.