Purpose To increase the number of people with disabilities in employment, we need to understand what influences employers’ hiring decisions. In this systematic review, we map out factors affecting employers’ hiring decisions about people with disabilities. Methods This study is a systematic review that applies the COM-B model to identify factors that contribute to employers (not) hiring people with disabilities. The COM-B model proposes that employers will perform hiring behavior (B) if they have the capability (C), opportunity (O) and motivation (M) to do so. We also investigate if factors have a negative, positive or no effect. We report in accordance with the PRISMA guidelines. Results In a review of 47 studies, we find 32 factors. Most of these factors are barriers. The most frequently mentioned barriers are employers’ (1) expectations that people with disabilities are unproductive, (2) expectations that people with disabilities cost a lot of money, and employers’ (3) lack of knowledge about disabilities. The most researched facilitators for employers to hire people with disabilities include (1) the motivation to help others, (2) working in a large organization, and (3) expecting a competitive advantage. The effect of factors can differ depending on contextual circumstances, including the type of organization, the type of disability and different policies. Conclusions We conclude that hiring decisions are influenced by an array of different barriers and facilitators. The effect of these factors can differ across organizations and disability types. Our study of factors affecting hiring can be used by scholars, policy makers, and organizations to create interventions to increase the hiring of people with disabilities