The present study examined the relationship between emotion malleability beliefs and daily positive affect (PA) and negative affect (NA) in adolescents. 639 participants provided information about emotion malleability beliefs and emotion regulation strategies on the first day of the study and six daily measurements of PA and NA. Emotion malleability beliefs had a positive relationship with PA and a negative relationship with NA. Higher emotion malleability beliefs predicted lower carryover effects of PA and NA across assessment days. We also found (...) that cognitive reappraisal might affect the relationship between emotion malleability beliefs and daily affect, such that those who held high levels of malleability beliefs were more likely to engage in cognitive reappraisal and report lower NA and higher PA. The findings of the present study suggest that emotion malleability beliefs could predicate daily emotions and emotion dynamics across days in adolescents. (shrink)