We designed and developed an emotion control treatment and investigated its effects on college students' academic emotions, motivation, and achievement in an online remedial mathematics course. The treatment group showed more positive emotions of enjoyment and pride than the control group. The treatment group also showed a higher level of motivation than the control group but there was no difference between the two groups in achievement. Implications for the design and development of interventions or systems for students' emotion control are discussed. (Contains 4 figures and 4 tables.)