Background: Bedside diagnosis of patent ductus arteriosus (PDA) continues to be important, especially when echocardiography is not readily available. Objective: The aim of our study was to evaluate whether measurement of left main bronchus displacement portrayed on a chest X-ray as a widened carina angle (CA) may support the presumptive diagnosis of PDA. Methods: Displacement of the left bronchus was assessed by measuring the angle between the two main bronchi at the level of the carina in 47 infants with PDA and 73 with no evidence of ductus, all born before 32 weeks of gestation. Results: The PDA group had a significantly wider CA (99.9 ± 12.1°) compared to the no-ductus group (72.9 ±15.7°; p < 0.001). Resolution of the PDA resulted in closure of the CA (62.3 ± 10.8°). We observed a significant and positive association between an increased CA measurement and PDA occurrence (OR = 1.7, 95% CI = 1.4–2.1). A CA cutoff point of 90° had the highest sensitivity (85%) and specificity (85%) for indicating the presence of PDA. Conclusions: Measurement of the CA is an easily accessible and reliable tool that may assist in establishing the diagnosis of PDA.