This study assessed the clinical efficacy of nirmatrelvir plus ritonavir (NMV-r) in treating patients with coronavirus disease-2019 (COVID-19) and substance use disorders (SUDs). This study included two cohorts: the first examined patients with SUDs, with and without a prescription for NMV-r, while the second compared patients prescribed with NMV-r, with and without a diagnosis of SUDs. SUDs were defined using ICD-10 codes, related to SUDs, including alcohol, cannabis, cocaine, opioid, and tobacco use disorders (TUD). Patients with underlying SUDs and COVID-19 were identified using the TriNetX network. We used 1:1 propensity score matching to create balanced groups. The primary outcome of interest was the composite outcome of all-cause hospitalization or death within 30 days. Propensity score matching yielded two matched groups of 10 601 patients each. The results showed that the use of NMV-r was associated with a lower risk of hospitalization or death, 30 days after COVID-19 diagnosis (hazard ratio (HR), 0.640; 95% confidence interval (CI): 0.543-0.754), as well as a lower risk of all-cause hospitalization (HR, 0.699; 95% CI: 0.592-0.826) and all-cause death (HR, 0.084; 95% CI: 0.026-0.273).However, patients with SUDs had a higher risk of hospitalized or death within 30 days of COVID-19 diagnosis than those without SUDs, even with the use of NMV-r (HR, 1.783; 95% CI: 1.399-2.271). The study also found that patients with SUDs had a higher prevalence of comorbidities and adverse socioeconomic determinants of health than those without SUDs. Subgroup analysis showed that the benefits of NMV-r were consistent across most subgroups with different characteristics, including age (patients aged ≥60 years [HR, 0.507; 95% CI: 0.402-0.640]), sex