This study aimed to determine whether left atrial (LA) enlargement was an independent risk factor for the patent foramen ovale (PFO)-attributable cryptogenic stroke (CS) and develop a nomogram to identify causative PFO. From September 2020 to September 2021, 64 patients with PFO-attributable CS and 128 age, sex, and hypertension status-matched non-stroke and non-migraine PFO patients were enrolled into the derivation cohort. The validation dataset consisted of 111 patients between October 2021 and May 2022 from the same institution. Significant characteristics of PFOs and cardiac functions in the multivariable conditional logistic regression were incorporated to develop a nomogram for recognizing high-risk PFO. PFO-attributable CS was independently correlated with LA diameter index (LADI)>23mm/m2. The nomogram for predicting causative PFO included large right-to-left shunt, small-angle PFO and LADI>23mm/m2. The derivation and validation groups had C-indices of 0.861 (95% CI: 0.803 – 0.919) and 0.766 (95% CI: 0.670 – 0.861), respectively. There was good consistency between the prediction and actual observation on the calibration curve. The decision curve analysis showed that the nomogram was clinically useful. PFO-attributable CS was independently correlated with LADI. The nomogram for predicting causative PFO was developed and will be useful in selecting suitable patients for PFO closure.