The policy--English as a medium of instruction (EMI)--in computing education plays an important role in achieving the outcomes of computer science programs. This study examines the effects of Saudi Arabia's English as a medium of instruction (EMI) policy in undergraduate computer science programs at public universities. Study data was collected from three samples: alumni records (n = 1,316), a questionnaire administered to current instructors (n = 42), and a questionnaire administered to current students (n = 250). A quantitative analysis was then performed on this data. Analysis of the alumni records shows that students' average grades in their English courses in the first year of their five-year program significantly predicted their overall grade point average (GPA). Analysis of the instructors' questionnaire showed that instructors had positive attitudes toward the EMI policy, and that most instructors believed that students' English proficiency does not limit their engagement and performance in class. Analysis of the current students' questionnaire demonstrated that students preferred to learn in Arabic, their native language. Furthermore, analysis of the students' questionnaire indicate that students' societal attitudes and self-efficacy significantly predicted their preferred language of instruction. The study concludes that instructors need to differentiate between students' English proficiency and their knowledge of computer science when assessing students' work, and that policymakers should consider students' preferred language of instruction when designing computer science curricula.