Background: The unimaginable power of emerging technologies has transformed education in terms of content creation and instructional design. Due to high value of AR/VR in education, teachers of the 21st century are expected to empower themselves professionally to be able to utilize these technologies in their instructional practices. Despite detailed examination of teachers' readiness for using AR in terms of perceptions, attitudes, and beliefs, very few studies have incorporated AR in teaching theoretical courses of graduate teacher education programs by utilizing constructivist pedagogical strategies. Objectives: The current study investigated the impact of a collaborative AR-enhanced learning environment on learning gains and technology implementation beliefs in a graduate teacher training course. Methods: Thirty-one in-service teachers participated in the study as the experimental (n=15) and control (n=16) groups. An AR app was developed for teaching 20 key concepts of the course Language Curriculum Design. The experimental group was instructed to work collaboratively with the app to learn the content, while the control group learned the concepts using the app in a lecture-based class. Learning gains were assessed by midterm and final exams and a term project. Results and Conclusions: The results showed that the experimental group outperformed the control group in learning the content and completing the project; and they had more positive technology implementation beliefs at the end of the experiment. Also, the participants were found to have positive attitudes towards the educational and pedagogical values of AR; and if the curricular and situational constraints are removed, they are highly motivated to use AR in their classes. Implications: The findings demonstrated the feasibility of incorporating AR technology into teaching abstract concepts in Art and humanities disciplines; and how teacher educators can benefit from integrating a collaborative approach with AR technology to teach advanced courses.