Undergraduate students are especially vulnerable to psychosocial distress (Center for Collegiate Mental Health, 2018), and the rate at which undergraduates are now seeking mental health services has far outstripped mental health infrastructure on college campuses (Prince, 2015). Increased utilization of time-limited group interventions has been shown to be a promising approach to managing the disparity between demand and availability of university mental health services (Shaffer, et al., 2017; Weatherford, 2017). Among time-limited group treatments, brief Self-Compassion (SC) interventions may be particularly promising tools for promoting resiliency and reducing psychosocial distress in undergraduates (Anderson, 2017, 2019; Arch et al., 2014, 2016; Dundas et al., 2017; Smeets et al., 2014). However, an examination of the literature revealed that there was no work focused on determining the processes (e.g., mediators and mechanisms) by which brief SC interventions function. Identifying mediators and mechanisms is critical to optimizing the effectiveness of interventions, and can help ensure that they create robust, lasting, beneficial change as expeditiously as possible. The current study sought to provide preliminary groundwork for future optimization of brief SC interventions by investigating a preliminary mechanism by which these interventions function that features two potential mediators: Common Humanity (CH) and Nonreactivity to Inner experience (NR). It was hypothesized that a text-enhanced SC intervention (ESC) would (1) predict changes in CH and NR, such that participants who received the ESC intervention would have significantly greater increases in CH and NR from baseline-to-posttest than those in a control condition, and (2) these changes in both CH and NR from baseline to post-treatment would mediate the relationship between the ESC intervention group and distress outcomes from post-treatment to follow-up. Specifically, changes in CH--but not changes in NR--were expected to mediate the relationship between the SC intervention and changes in self-judgment from post-treatment to follow-up; in contrast, it was hypothesized that changes in NR--but not changes in CH--would mediate the relationship between the ESC intervention and changes in anxiety from post-treatment to follow-up. Finally, it was hypothesized (3) that the role of CH as a mediator of the association between SC intervention and self-judgment would be moderated by baseline NR such that mediation would be stronger for those with higher baseline NR scores than for those with lower baseline NR scores. Data from 118 undergraduate students from two separate randomized control trials (RCTs) examining the ESC intervention (Anderson, 2017; Anderson, 2019) were combined in the current study. Results revealed that the ESC intervention led to significantly greater increases in CH, but not NR. However, the results of the current study failed to find support for any mediation hypotheses, or evidence of a preliminary moderated-mediation mechanistic process. The results bolster and expand on existing literature (Anderson, 2017; Smeets et al., 2014) demonstrating the ability of brief SC interventions to increase CH. The results also provide guidance and important next steps for future identification of mediators and mechanisms of brief SC interventions. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]