This article summarizes a quantitative study of the effects of animated agents in web-based instruction (WBI) on mathematics achievement and attitudes toward mathematics in postsecondary education. Eighty-one college students who were enrolled in a core mathematic course at a doctoral/research-extensive university in central Alabama participated in this study. Using a pretest-posttest control group design model, the study verified that the presence of animated agents in WBI can improve postsecondary students' mathematics achievement and attitudes toward mathematics. In addition, the interaction of gender choice of the animated agent with several demographic factors did statistically affect attitudes toward mathematics. These findings can be used to better design, develop, and implement a web-based tutorial that promotes positive attitudes toward learning mathematics and long-term mathematics achievement in postsecondary mathematics.