This study focused on the complementary use of web-based learning in relation to first-semester college students' academic transition at a Chinese university. Through qualitative analyses it revealed that the technological affordances of web-based learning reified themselves in diverse forms and in a spatial-temporally unconstrained manner. Against its technological affordances, web-based learning offered students additional knowledge that complemented or enhanced their knowledge repertoires constructed in the classroom. This helped them make the academic transition, which may have been hindered by limited in-class time to meet individual needs and college-level standards. Meanwhile, mediated assistance, especially the instructor's constant adjustment of the instructional design to address the students' learning issues, interacted with the learning outcomes perceived by the students through web-based learning, which further buttressed their academic transition.