This study investigated the effects of a co-teaching training program on female pre-service teachers of special education at the Faculty of Education, King Saud University. It also examined whether the participants' academic majors affected their total knowledge gains obtained from the administered training program. A co-teaching training program was designed to train the assigned participants of the study on the main principles of co-teaching. Fifty-one female pre-service teachers were randomly selected to receive the co-teaching training program for six sessions. They studied in four different academic majors: behavioral disorders, mental disabilities, learning difficulties, and deaf and hearing impaired. A pre-measurement scale was administered prior to the treatment and immediately after the treatment to see the possible knowledge gains from the program. Results revealed significant improvements in the students' knowledge from pre-treatment to post-treatment. However, no statistically significant differences among the participants could be ascribed to the participants' academic majors. Recommendations, limitations, and tips for future studies have been provided.