Background: Transcatheter closure of atrial septal defect (ASD) has become the treatment of choice for most patients. About 5% of them suffer from transient headache episodes (THE) after the procedure, whose etiology is unclear., Aims: To evaluate risk factors for THE occurrence after transcatheter closure of ASD in the pediatric population., Methods: Eight hundred and forty patients, after transcatheter ASD closure with nitinol devices, from a single center, were included in retrospective analysis. THE was defined as occurring up to 24 hours after the procedure. A logistic regression model including age, weight, ASD diameter, device size, presence of nitinol coating on the device, fluoroscopy time, application of balloon calibration, device oversizing, and residual shunt after 24 hours was created to evaluate risk factors for THE occurrence., Results: There were 40 patients with THE (4.8%), 70% female and 30% male. The median age was 13 (7.35-16) years. In patients with headache, balloon calibration (BC) was performed more frequently (82.5% vs. 43.3%; P <0.001). The balloon waist median (interquartile range [IQR]), 19 (16-22) mm vs. 15 mm (12-18) mm (P <0.001), and device size median (IQR), 18 (13.5-22) mm vs. 14 (11-17) mm (P <0.001) were larger, and residual shunt after 24 hours (12.5% vs. 4.9%; P = 0.03) and a year (7.5 vs. 1.0%; P <0.001) were more frequent. ASD size and the prevalence of double/multiple ASD were similar in both groups. Age, BC application, no nickel release protection, duration of fluoroscopy, and device oversizing were predictors of THE (P <0.001)., Conclusions: BC during percutaneous ASD closure and the lack of a protective layer against nickel release on the device are risk factors for headache occurrence in the early postprocedural period.