Co-teaching has historically been used in K-12 education to provide students with disabilities access to general curriculum; therefore, much of the co-teaching literature has focused on the K-12 population. Research on collegiate co-teaching has been more limited and largely focused on the advantages and disadvantages of co-teaching, omitting important factors that affect relationships between partners. This qualitative study involved seven interviews of co-teachers of graduate and undergraduate classes in order to better understand interactions between college-level co-teaching dyads. Data analysis revealed themes of power and authority structures, dynamics of co-teaching relationships, and co-teachers' perceptions related to advantages of co-teaching, disadvantages of co-teaching, and student experiences. The researchers developed the Circular Model of Collegiate Co-Teaching, an original model to explain how these themes and subthemes are interrelated and affect each other. Specific best practices and new insights for collegiate co-teaching practice are discussed.