Objective <p>Nonsuicidal self-injury (NSSI) is a significant predictor of suicide, particularly among patients with borderline personality disorder (BPD). This study examined modifiable psychological factors associated with NSSI to generate preliminary insights that may inform future intervention research.</p> Methods <p>In a cross-sectional design, 109 female BPD patients completed self-reported measures assessing NSSI behaviours, mindfulness skills, emotion regulation strategies, depressive symptoms, and self-compassion. Correlational analyses were conducted to investigate the relationships among the psychological variables, NSSI frequency, and the number of NSSI methods used. Ordinal logistic general linear models were used to identify potential predictors of NSSI frequency.</p> Results <p>Participants reported low levels of self-compassion, mindfulness skills, and self-esteem, alongside high depression, impulsivity, and frequent self-harming behaviour. The key relevant psychological factors associated with more frequent NSSI included increased impulsivity (95% CI: 1.007–1.199), higher scores on the adaptive cognitive-emotional regulation strategies subscale (95% CI: 1.015–1.082), and reduced self-compassion (95% CI: 0.945–0.999). Although mindfulness skills were not directly linked to the frequency of NSSI or the number of methods used, they were moderately correlated with these risk factors.</p> Conclusions <p>These findings underscore the importance of targeted interventions for NSSI in BPD patients. Mindfulness-based approaches may reduce suicide risk and improve treatment engagement by addressing deficits in impulsivity, acceptance, and self-compassion.</p> Clinical trial number <p>Not applicable (this study was a cross-sectional, observational design and does not meet the criteria for a clinical trial). The project and data are publicly registered at: <a href="https://doi.org/10.17605/OSF.IO/ZUR84">https://doi.org/10.17605/OSF.IO/ZUR84</a></p>