 This paper examined the validity and reliability of the mentoring competency assessment, MCA, a tool designed to measure mentoring skills among post-secondary STEM researchers. The authors found that the MCA has strong psychometric properties, including a five-factor structure and high internal consistency. They also identified five items that could be removed without affecting the overall validity of the tool. This article was authored by Sohee Heung, Jenna G. Rogers, Stephanie Seahouse, and others.