Past research has consistently shown that there is a relation between personality and academic performance, but much less work has focused on explaining this relation. The present study examined whether three aspects of homework behavior, namely homework time, procrastination, and learning strategies, mediate the relation between personality and academic performance, controlling for cognitive ability, track level, gender, and ethnicity. We investigated this in a nationally representative sample of about 9000 secondary school students in The Netherlands (average age 13 years). Results indicated that all personality traits were related to homework behavior, and that both personality and homework behavior were related to end-of-year grades in math and Dutch language. Nevertheless, homework behavior only partially mediated the relation between personality and grades. (Contains 6 tables.)