<p>Research has begun to establish a negative relationship between non-suicidal self-injury (NSSI) with trait self-compassion and trait mindfulness, highlighting the potential protective utility of these traits. However, examining mindfulness facets and self-compassion dimensions with key functions that underlie NSSI remains largely unexplored. This study investigated the relationship between mindfulness facets and the self-compassion dimensions (compassionate self-responding [CS] and uncompassionate self-responding [UCS]), with key NSSI functions (affect regulation and self-punishment) and NSSI behaviors (history and versatility). Participants were 273 adults with and without a history of NSSI (80.2% women, <i>M</i>_<i>age</i> = 34.45, <i>SD</i>_<i>age</i> = 13.18) who completed self-report measures of NSSI, trait self-compassion, and trait mindfulness. Pearson’s correlation analysis found significant associations between self-compassion dimensions and mindfulness facets (act with awareness, describe, nonjudge, and nonreact) with a history of NSSI. Results indicated that UCS and the describe facet negatively predicted NSSI history, while only act with awareness negatively predicted versatility. In terms of function, the nonjudge (positive association) and describe (negative association) facets predicted the affect regulation function of NSSI, while UCS predicted the self-punishment function. This study provides a more nuanced picture of the relationship between trait mindfulness and trait self-compassion with engagement in NSSI. Overall, results suggest that although lower reports of mindfulness facets are negatively linked to NSSI history, difficulties in describing thoughts and emotions may be linked to the affect regulation function of NSSI. The findings may suggest teaching self-compassion-based skills may be beneficial for individuals who engage in NSSI if self-punishment serves as an underlying function.</p>