Engineering identity is a crucial element in the formation of engineering students. It represents how strongly a student identifies with being an engineer and indicates persistence and retention in engineering. Many factors influence the development of an engineering identity; for example, students from diverse backgrounds (transfer, first-generation, one with a disability, female, or minority students) may face challenges in performance expectations, resource access, and peer interactions. Such experiences can hamper their engineering identity development, retention, and advancement in engineering. These challenges also manifest in engineering teamwork, where students are expected to apply and acquire engineering skills, assert themselves, and navigate unfamiliar team dynamics.Many engineering education studies have stressed the importance of teamwork training in undergraduate engineering education. They have investigated how teamwork experiences promote learning, technical communication, metacognitive ability, social-technical thinking, and other skills. However, little is known about how teamwork informs or is informed by students' engineering identities. Understanding the connection between teamwork and the engineering identity of diverse students, especially among underrepresented groups, enables instructors to create inclusive teaching and learning environments. Such learning environments improve student performance and promote interest and recognition, which are crucial to a student's professional formation.Funded by the Research Initiation in Engineering Formation (RIEF) program of the National Science Foundation, our project aims to (1) depict teamwork experience through the behaviors of and disagreements between team members in a highly diverse engineering student population at a four-year Hispanic Serving Institution;. and (2) understand how teamwork experience informs students' engineering identities using a mixed-methods approach. During the first year of the project, the research team designed a survey instrument and an interview protocol to measure students' engineering identity and teamwork experiences. Survey and interview data has been collected from 18 engineering classes. Our mixed-methods approach consisted of quantitative and qualitative methods. This paper summarizes the preliminary results and initial findings of this study.