Transseptal catheterization (TC) is routine in electrophysiology and structural heart procedures. TC can be technically challenging due to a thick or scarred septum. Intracardiac echo (ICE) and Radiofrequency (RF) has helped in the success of TC. We report the first case of concomitant Atrial Fibrillation (AF) ablation with Left Atrial Appendage Closure (LAAC) with atrial trans-septoplasty (ATS). N/A A 63-year-old male with drug-refractory paroxysmal AF, CHADS Vasc Score of 6, and recurrent epistaxis presented for concomitant AF ablation and LAAC implant. ICE demonstrated a very thick septum of 1.2 cm without sparing of the fossa ovalis. Following transseptal (TS) puncture using RF needle, the TS sheath could not be advanced to the Left atrium (LA) despite different approaches including the use of a stiff pigtail wire in the LA, extra stiff wire in the right and left superior pulmonary vein (LSPV), and sequential dilation with progressively larger diameter long dilators. Successful ATS was performed under ICE and fluoroscopy guidance using a non-compliant 8 x 20 mm balloon over a stiff wire in the LSPV as shown in the figure, allowing access of a 14 Fr cryosheath into the left atrium. Pulmonary veins were successfully isolated using the cryoballoon. After the exchange of a Watchman (WM) sheath, a WM FLX device was successfully implanted under ICE and fluoroscopy guidance. ATS can be safely performed in difficult TC due to a thick septum. The balloon used for ATS can be selected based on the diameter of the transeptal sheath required to complete the procedure. Additional studies are needed to evaluate the long-term effects of this technique.