DescriptionIn an effort to meet the needs of special education students in inclusion classrooms co-teaching is typically utilized as a service delivery model. Research has identified a number of benefits to co-teaching however, a number of obstacles have been found to inhibit its effective implementation in secondary schools. High school special education co-teachers have been found to have an inferior role in their co-teaching relationships and co-teachers have been found to lack the skills needed to collaborate effectively as a team. Teamwork has been an area of focus for the health care and business industry but a focus on team-building in K-12 education has been lacking. This study involved the implementation of a team-building professional development series for high school co-teachers. The professional development included activities meant to enhance communication, problem solving, collaboration, and trust for co-teachers. The study examined the influence participation in the professional development had on co-teaching relationships. This study utilized a mixed-methods approach and included interviews, surveys, questionnaires, and observations as data collection methods. The overall findings of this study demonstrate that the majority of teachers have positive perceptions of co-teaching and find it beneficial for both teachers and students. Teachers expressed a number of frustrations regarding how administrators approach the practice of co-teaching. Co-teachers want administrators to be more respectful of co-teaching and take their needs into account when creating schedules and providing professional development. Participants of this study had varying degrees of satisfaction in their co-teaching dynamic prior to the start of this professional development. All participants described having a positive experience in the professional development. Participants expressed that team-building has a positive impact on co-teacher relationships and should be provided to pairs before the school year starts. There was a range in the degree of impact the professional development had on participants. Many felt that since their relationship was already positive, they did not experience drastic changes. Others felt they made progress and are optimistic for continued growth. Some pairs saw slight changes in their dynamic and felt that circumstances beyond their control impacted their ability to work as a team.