Early aspirin (ASA) use after orthotopic heart transplantation (OHT) has been associated with lower rates of cardiac allograft vasculopathy (CAV). We hypothesized that the inverse association between ASA use and CAV incidence may be most pronounced in patients with allograft rejection. Patients receiving OHT at a single center 2004-2010 (n = 120) were categorized by early ASA use post-transplant (ASA use for > 6 months in the first year) and the presence of biopsy-defined acute cellular rejection (ACR) and/or antibody-mediated rejection (AMR) during 5-year follow-up. Propensity scores for ASA treatment were estimated using boosting models and applied by inverse probability of treatment weighting. The association between ASA use and time to moderate/severe CAV (ISHLT ≥ 2) was investigated. Among patients with ACR or AMR, ASA therapy was associated with significantly lower rates of CAV≥ 2 (3.3 vs. 30.1%; P = .001; HRadj .07; 95% CI .01-.52), whereas ASA therapy was not associated with lower rates of CAV in patients with no rejection (5.6 vs. 5.3%; P = .90; HRadj 1.26; 95% CI .08-20.30; pinteraction  = .09). Early ASA use after OHT was associated with lower rates of moderate to severe CAV only in those patients with episodes of allograft rejection.