Objectives <p>In order to improve the effectiveness of mindfulness-based interventions (MBIs), it is critical to identify and target modifiable affective constructs that reduce depression symptoms, particularly given the effectiveness of MBIs for reducing depression symptoms, preventing relapse, and promoting wellbeing.</p> Method <p>The present study evaluated affective patterns in college students (<i>n</i> = 127) with elevated depression symptoms who participated in an 8-week randomized controlled trial (RCT) of a technology-delivered mindfulness-based intervention (tdMBI). Mediation analyses were conducted to evaluate the role of affect (e.g., positive affect, negative affect, and emodiversity) in facilitating a reduction in depression symptoms during the RCT.</p> Results <p>Only change in positive affect significantly mediated the relation between RCT intervention group and depression symptoms, such that an increase in positive affect was distinctly related to reduced depression symptoms for the intervention group. Changes in global and positive emodiversity were related to change in depression symptoms, but none of the emodiversity metrics were significant mediators.</p> Conclusions <p>The present study illustrated that increased positive affect had a distinct role in reducing depression symptoms in college students. Future research should strive to further understand how specific mindfulness-based strategies and interventions might function to increase the capacity for experiencing positive affect for individuals with depression.</p> <p>Preregistration.</p> <p>This study was pre-registered with Open Science Framework: <a href="https://osf.io/suqp7/?view_only=f761750f6fa14bf3ad2a56e21b2e9fbd">https://osf.io/suqp7/?view_only=f761750f6fa14bf3ad2a56e21b2e9fbd</a></p>