A team of engineering faculty at the University of Illinois at Urbana-Champaign created an integrated teaching and leadership development program in 2016 after realizing the need for both pedagogical training and leadership education for graduate teaching assistants (GTAs). Training in teaching and leadership at the graduate level are often separated even though the skills needed for good teaching are highly transferable, and many are nearly identical to skills possessed by good leaders. Through this program, GTAs are expected to develop teaching skills as well as leadership skills. Each session in the program provides context in applying leadership skills in their day-to-day duties as a teaching assistant. This program is bringing collaboration across campus with speakers from other non-engineering units, such as the campus-level teaching and learning center, the campus-level leadership center, and the Department of Theatre. Industry speakers are also invited to provide a workplace perspective, with two corporate representatives and a group of local technology entrepreneurs presenting in the past year. Four of the largest engineering departments have since joined the initiative by requiring their new GTAs to complete the program as part of their on-boarding process. With an initial cohort of 13 graduate students in Spring 2017, the program has now grown to over 190 in Fall 2019. To assess the perception of transferability between teaching skills and leadership skills among participants in the program, a comparison group versus treatment group study was conducted in Fall 2018. The comparison group is comprised of new engineering GTAs who did not participate in the program and the treatment group is comprised of participants in the program. This paper will present the result of the study and discuss lessons learned from implementing an integrated teaching and leadership development program.