Brief and cost-effective interventions teaching emotion regulation techniques can be feasibly applied to promote mental health in University students. The tools of mindfulness (i.e., objective awareness and acceptance) and positive reappraisal (i.e., positive re-evaluation of negative events) can mutually benefit one another to promote well-being. The current study explored the effects of a randomly-assigned Mindful-Reappraisal intervention (n=36) compared to Reappraisal-Only (n=34) and an active control (n=36) on university students' daily affect over five days. Time by condition interactions were analyzed with planned contrasts and multilevel growth modelling.