The collaborative nature of citizen science raises important questions about managing ownership of its research outputs. Potential citizen science research outputs include data sets, findings, publications, and discoveries of new ideas, methods, products, and technologies. Unlike citizen science projects conducted in other disciplines, biomedical citizen science projects often include features, such as contribution of personal health data, that might heighten citizen scientists’ expectations that they will be able to access, control, or share in the benefits of project outputs. Here, we refer to moral claims of access, control, and benefit as ownership claims, and a project’s management of ownership claims as its ownership practices. Ethical management of ownership is widely recognized as an important consideration for citizen science projects, and practitioners and scholars have described helpful recommendations for preempting issues and engaging stakeholders on practices. Building on this literature, we propose a framework to help biomedical citizen science projects systematically evaluate the ethical soundness of their ownership practices based on four considerations: reciprocal treatment, relative treatment, risk-benefit assessment, and reasonable expectations.