Background Donor-to-recipient lung size matching at lung transplantation (LTx) can be estimated by the predicted total lung capacity (pTLC) ratio (donor pTLC/recipient pTLC). We aimed to determine whether the pTLC ratio is associated with the risk of primary graft dysfunction (PGD) after bilateral LTx (BLT). Methods We calculated the pTLC ratio for 812 adult BLTs from the Lung Transplant Outcomes Group between March 2002 to December 2010. Patients were stratified by pTLC ratio >1.0 (oversized) and pTLC ratio <1.0 (undersized). PGD was defined as any ISHLT Grade 3 PGD (PGD3) within 72 hours of reperfusion. We analyzed the association between risk factors and PGD using multivariable conditional logistic regression. As transplant diagnoses can influence the size-matching decisions and also modulate the risk for PGD, we performed pre-specified analyses by assessing the impact of lung size mismatch within diagnostic categories. Results In univariate analyses oversizing was associated with a 39% lower odds of PGD3 (OR 0.61, 95% CI, 0.45-0.85, p = 0.003). In a multivariate model accounting for center-effects and known PGD risks, oversizing remained independently associated with a decreased odds of PGD3 (OR 0.58, 95% CI 0.38 to 0.88, p = 0.01). The risk-adjusted point estimate was similar for the non-COPD diagnosis groups (OR 0.52, 95% CI 0.32 to 0.86, p = 0.01); however, there was no detected association within the COPD group (OR 0.72, 95% CI 0.29 to 1.78, p = 0.5). Conclusion Oversized allografts are associated with a decreased risk of PGD3 after BLT; this effect appears most apparent in non-COPD patients.