Past research into the relationship between English proficiency test (EPT) scores and score profiles, such as the IELTS and the TOEFL, has shown that there is not always a clear relationship between those scores and students' subsequent academic achievement. Information about students' academic self-concept (ASC) may provide additional information that helps predict future academic success. Research has consistently shown a positive relationship between students' ASC and subsequent academic achievement and educational attainment in both school and higher education settings. The purpose of the current study was to examine the relationship between the academic performance of international students and their language proficiency and academic self-concept as well as other characteristics related to academic success. The study focused on first year international students in undergraduate business programs at an English-medium university in Canada. The following information was collected about the student participants: grades in degree program courses, annual GPA, and EPT scores (including subscores). In addition, students completed an academic self-concept scale. To obtain additional information about success in first-year business courses, instructors in two required courses were interviewed about the academic and language requirements in their courses and the profile of successful students. Correlations between the students' course grades, GPA, EPT scores, and ASC score were calculated. The instructor interviews were analyzed using a content analysis procedure. The findings from all data sources were triangulated and show that language ability, ASC, and other factors impact academic success during the first year in a business program. The implications of these findings are discussed.