Research has shown that trait mindfulness is associated with greater emotion differentiation, particularly, differentiation of negative emotions. Little research however has examined mechanisms underlying this relationship. In this study, we tested two mediation pathways. Emotion regulation has been predicted to play a key mediating role, but the evidence has been limited and inconclusive. In addition, we propose a different pathway, involving appraisals, which the literature has overlooked. We propose that the relationship between mindfulness and negative emotion differentiation can also be accounted by appraisal differentiation. Individuals who are low on appraisal differentiation are prone to making mixed appraisals on distinct appraisal dimensions, such that they do not have clear interpretation of events. Three hundred and ninety undergraduate participants reported their current emotions, coping styles, and appraisals up to 36 times across 2 days. Analyses revealed that both maladaptive emotion regulation and appraisal differentiation were significant mediators of the relationship between mindfulness and emotion differentiation. The findings suggest that less mindful individuals experience undifferentiated negative emotional states not only because they tend to use ineffective regulatory strategies, but also because they tend to see the world in a manner characterized by many different competing appraisals.