This study contributes to team science and competency development by comparing demonstrated teamwork skills by engineering students participating in disciplinary and cross-disciplinary team projects. Teamwork skills are key competencies necessary to solve complex technical challenges in the workplace. Despite prior efforts to enhance these competencies in engineering students, there is still a lack of empirical research examining the effectiveness of such efforts. This study compares teamwork skills demonstrated by undergraduate engineering students in two conditions: 1) engineering-only teams and 2) cross-disciplinary collaboration with education students. Projects in both settings had similar levels of complexity, scope, team size, and requirements. The differences in teamwork skills were investigated using a mixed methods approach with a main quantitative phase, followed by a secondary qualitative analysis to further examine the nature of the differences. Students in the cross-disciplinary model demonstrated higher levels of teamwork skills than those in the engineering-only condition. Results from this work illustrate how authentic and well-designed cross-disciplinary team projects can facilitate the development of students' teamwork skills beyond what can be achieved in disciplinary teams, fulfilling an essential ABET requirement and enhancing student preparation to succeed in the workplace.