Introduction: Domestic violence (DV) and sexual assault (SA), together called sexual and gender-based violence (SGBV), are traumatic and life-changing events. Post-assault follow-up care is essential for survivor recovery through medical care, mental health functioning, and injury reassessment. The objective of this analysis was to determine the frequency of loss to follow-up (LTFU) in a SGBV population, and the characteristics most commonly associated with LTFU. Methods: The Sexual Assault and Partner Abuse Care Program (SAPACP) is the only Ottawa program for emergency/forensic care. Demographic and assault characteristics were abstracted from the SAPACP clinical case registry (1 Jan 2015 to 20 Dec 2017). Descriptive analyses and bivariable/multivariable logistic regression modelling assessed factors most strongly associated with LTFU using odds ratios (OR), adjusted OR (AOR), and 95% confidence intervals (CI). Results: Among 894 initial SAPACP visits, 482 (53.9%) were LTFU. Of those LTFU, 445 (92.3%) were female, 185 (38.4%) arrived by ambulance, 284 presented acutely (58.9%), 70 (14.5%) had substance use issues, and 82 (17.0%) were re-victimized. There were 229 (47.5%) sexual assaults, 201 (41.7%) physical assaults, and 92 (19.1%) verbal assaults. LTFU patients were more likely to arrive by ambulance (AOR: 1.09, 95% CI: 1.34-2.69), experience re-victimization (AOR: 1.94, 95% CI: 1.25-3.03), and have a substance use disorder (AOR: 1.67, 95% CI:1.02-2.73). Those more likely to attend follow-up included sexual assault survivors (AOR: 0.37, 95% CI: 0.27-0.50) and acute presenters (AOR: 0.58, 95% CI: 0.44-0.78). Conclusion: Over half of patients arriving for initial SAPACP visits did not follow-up. LTFU was more likely among cases that arrived by ambulance, and those involving revicitimization or substance use disorders. Follow-up is critical for maintaining mental and physical health post-trauma. While some characteristics increased follow-up likelihood, this study has identified groups that need attention to reduce LTFU.