Successful emotion regulation is a critical component of mental health, and difficulties with emotion regulation have been associated with a wide range of disorders including anxiety and depressive disorders. However, although much is known about commonly used forms of emotion regulation such as cognitive reappraisal and expressive suppression, the relative contribution of two important facets of emotion regulation – frequency and self-efficacy – is not yet clearly established. To address this issue, we conducted two studies. Study 1 employed a community sample (cross-sectional N=431; four-to-five-month longitudinal N=182). Study 2 employed a clinical sample (cross-sectional N=132). Both assessed emotion regulation frequency and self-efficacy, as well as affective outcomes (anxiety and depressive symptoms). Findings indicated cognitive reappraisal self-efficacy appears to be a relevant variable understanding negative affect outcomes, cross-sectionally, longitudinally and in the clinical sample. Our findings support the process model of emotion regulation in affective symptomatology. Implications for theory and treatment are discussed.