Students in science and engineering (S&E) are preparing for careers in fields where international partnerships are increasingly important to advancing knowledge and discoveries. It has been over a decade since the National Science Board (NSB) highlighted the importance of international collaboration and called for increased government commitment to promoting international S&E research and education. NSB called for the National Science Foundation (NSF) to take a leadership role in international S&E research and education activities promoting "…increased participation in international S&E activities by younger U.S. scientists and engineers from diverse backgrounds, especially those in the early stage of their careers, in order to develop an internationally competitive and globally-engaged S&E workforce." NSF's East Asia and Pacific Summer Institutes (EAPSI) program, which provides international fellowships to U.S. graduate students in S&E, is one program that helps to further NSF's commitment to support the active engagement of early career S&E researchers in international collaborations. NSF contracted with Abt Associates to conduct an evaluation of the EAPSI program to investigate whether it was meeting its goal of providing U.S. graduate students with international experiences that will enable future collaboration with foreign peers. This report summarizes the findings from that evaluation, which was designed to investigate the characteristics of EAPSI applicants and their motivations for participation, the host researchers' motivations for participating in the program, participants' experiences in and perceptions of the program, and outcomes of the program.