Objective In DSM-5, non-suicidal self-injury (NSSI) and suicide attempts (SA) are classified as distinct disorders in the section of conditions for further study. However, some have questioned the validity of distinguishing NSSI from SA. The objective of this study was to longitudinally examine the correlates, discharge disposition, and rate of re-presentation to emergency services of adults who engaged in NSSI and compare them to (a) adults who engage in SA and (b) adults with no self-harm or suicidal ideation (SI). Method Data came from 4,772 presentations to adult psychiatric services in the emergency departments of tertiary care hospitals in Winnipeg, Canada between January 2009 and June 2012. Chart reviews were conducted for all presentations with NSSI (n = 158), and a sample of those with SA (n = 172) and no SH or SI (n = 173). Results Among the adults who returned to emergency services, those who originally presented with SA re-presented significantly sooner than those who presented with NSSI. (χ2(1) = 7.457, p = 0.006). Those who originally presented with NSSI that returned to hospital did not return with repeat NSSI, but instead the majority re-presented with suicidal thoughts and SA. Further, those who re-presented with NSSI and SA were less likely to be hospitalized or to receive a referral to mental health services, and more likely to be discharged to usual care at time of initial presentation. Conclusions Overall, these findings indicate a trajectory of escalation of self-harm behavior for certain people who engage in NSSI, especially those who re-present to emergency services.