Emotion malleability beliefs (EMB) have been shown to be a potential predictor of cognitive reappraisal use. However, the nature of the relationship between EMB and cognitive reappraisal use remains unclear. The present study manipulated EMB with an online intervention and measured participants’ EMB and cognitive reappraisal before the intervention as well as at three follow-ups. Eighty-six late adolescents who scored in the bottom 50% on EMB in a previous investigation were randomly assigned to the intervention group (increasing EMB) and the (...) control group. The intervention significantly increased EMB, and this effect remained one week and one month after the intervention. More importantly, the results showed that the lag paths from a previous measure of EMB on later cognitive reappraisal were positive and significant. The cross-lagged paths from cognitive reappraisal to EMB were not significant. The intervention to increase EMB showed significant indirect effects on cognitive reappraisal via EMB. The findings not only support that the intervention of EMB had a sustained effect but also evidenced that EMB had a causal effect on cognitive reappraisal. This suggests a promising way to enhance cognitive reappraisal for application in the treatment of clinical emotion disorders. (shrink)