Background: Bronchiolitis obliterans syndrome (BOS) is delayed allograft deterioration after lung transplant (LTX) that is clinically characterized by ≥ 20% decline from the baseline value of forced expiratory volume during the first second (FEV1). BOS is still a major obstacle limiting long-term survival post-LTX. The main aim of this study was to determine the predictors of BOS and death in Iranian LTX recipients. Materials and Methods: This retrospective cohort study included 44 LTX recipients who survived ≥ 3 months post-LTX at the Masih Daneshvari Hospital, Tehran, Iran from 2000 to 2014. The outcome was time from lung transplantation to BOS and/or death (due to all causes except BOS). We used competing risks analysis to assess the effect of other factors on the cumulative incidence function of BOS and death. We applied a Fine and Gray model with Bayesian approach. Results: The recipients’ age (Mean ± SD) was 36.7 ± 14.5 yr. 11 (25%) recipients developed BOS as the first event within the first five years post-LTX and 13 (30%) died due to all causes except for BOS. Our results showed that CMV infection was associated with a significant increase in risk of developing BOS [hazard ratio (HR) 1.22 (95% credible set: (1.01, 3.2)] controlling for other variables. Bilateral transplantation [HR (95% credible set): 2.4(1.51, 4.05)] and CMV infection [HR (95% credible set): 2.02 (1.67, 2.55)] were predictors of the mortality risk. Conclusion: CMV infection was a predictor of BOS risk in the studied patients. Moreover, bilateral transplantation and CMV infection were significant predictors of mortality in the present sample. Multi-center studies with larger sample sizes are required to better study the other risk factors, and the pathophysiologic mechanisms of BOS.