This study aimed to examine the effect of four types of assessment on overall student success in an online college-level climate change course. Quizzes, midterms, lab assignments, and a capstone project as well as knowledge check questions were used to assess different aspects of student learning, consistent with Bloom's taxonomy hierarchy. Quizzes and midterms assess basic knowledge, including remembering and understanding concepts, laboratory assignments require students to analyze and integrate concepts, and the capstone allows students to evaluate their understanding and create new content. Binary logistic regression, multiple regression analysis, continuous-by-continuous interaction modeling, and path analysis were used to investigate the moderating and mediating effects of these assessment types. We found both direct and indirect positive interactions as well as one negative interaction. Positive interactions were identified between quiz and lab assignment achievement and between capstone achievement and lab assignment achievement. The total score for correctly answered knowledge check questions positively affected quiz and lab assignment achievements. The interaction between capstone project achievement and total score for correctly answered knowledge check questions showed a negative interaction. Finally, the total score for correctly answered knowledge-check questions had an indirect positive effect on overall student success in the course. Results show that different types of assessment in an online course are complementary and amplify student learning.