Objective: To prospectively study the techniques and outcomes of transcatheter closure of complex Atrial septal defects (ASD). Study design and settings: Prospective single center study with experience in catheter closure of ASD. All patients with complex ASD suitable for device closure. Objective: Analysis of outcomes of transcatheter closure of complex ASD in JIPMER Hospital over the past 5-year period. Methods: Complex ASD was predefined and patients satisfying inclusion and exclusion criteria are included. All the patients had meticulous Transesophageal echocardiography (TEE) imaging beforehand. Modifications of the conventional techniques were allowed on a case per case basis according to operator preference. Successfully intervened patients were followed up clinically. Results: Out of the 75 patients enrolled, 69 patients had successful device closure (success rate 92%) despite challenging anatomy. Fifty-six (74%) patients had ASD ≥25 mm. Fifteen patients (20%) had defect size ≥35 mm and 20 patients (26.6%) had devices implanted with ≥35 mm waist size. Fifty percent of patients had complete absence of aortic rim and 25% had deficient posterior rim. Twenty percent of patients had malaligned septum. Mean follow up period was 3.2 years. Conclusions: Trans catheter closure is feasible in anatomically complex substrates of Secundum ASD. Careful case selection, scrupulous imaging protocol, and expertise in modified techniques are mandatory for successful outcomes.