We examine correlates and predictors for implicit associations with non-suicidal self-injury (NSSI) with the Self-Injury Implicit Association Test (SI-IAT) in a treatment-seeking sample. We also examine group differences in the SI-IAT among those with low/none, moderate and high/clinically significant borderline personality disorder (BPD) symptomatology in a treatment-seeking sample. Participants (N = 111; 58% female; 89% White; Mage = 30.25) completed the SI-IAT and self-report measures at two time points. Higher BPD symptom scores were significantly, positively correlated with implicit identification with NSSI, and predicted NSSI identity when controlling for depression indices, history of NSSI and other covariates. With Time 1 SI-IAT scores entered as a covariate, BPD scores no longer significantly predicted Time 2 SI-IAT scores. Individuals with moderate and high/clinically significant symptom counts of BPD had higher/stronger implicit associations with NSSI identity than those with no/low BPD symptoms. Individuals with symptoms of BPD may implicitly identify with NSSI more than other clinical groups; examination of implicit assessments in BPD in future research is needed to further explore implicit identification with NSSI in this patient group to further understand both cross-sectional and prospective relations.