In this study, we examined racial/ethnic differences in grade point average (GPA) among students at a highly selective, private university who were surveyed before matriculation and during the first, second and fourth college years, and assessed prominent explanations for the Black-White and Latino-White college achievement gap. We found that roughly half of the observed gap was attributable to family background characteristics and pre-college academic preparation. Of the within-college factors we considered, perceptions of campus climate and selection of major field of study were most important in explaining racial/ethnic differences in GPA. Personal resources, such as academic effort, self-esteem and academic identification, and patterns of involvement in campus life were significantly associated with GPA, but these factors did not account for racial/ethnic differences in academic performance. Overall, our results suggest that efforts to reduce the college achievement gap should focus on assisting students with the process of selecting major fields of study and on fostering a welcoming and inclusive campus environment.