Abstract Background Transseptal puncture (TSP) for catheter ablation (CA) of left-sided tachycardias is traditionally performed with the aid of fluoroscopy. Compared to fluoroscopy, intracardiac echocardiography (ICE) can provide better orientation and imaging of soft tissue structures that are relevant to TSP. Objective Our aim was to evaluate feasibility and safety of ICE-guided TSP in CA treatment of left-sided tachyarrhythmias. Methods Consecutive fluoroless CA procedures with combined use of three-dimensional electroanatomic mapping system and ICE requiring TSP were evaluated in 357 patients (269 male, mean age 54 ± 18 years) referred to our hospital from July 2014 to November 2018. Among CA treated left-sided tachyarrhythmias 55 patients had accessory pathway, 16 had focal atrial tachycardia, 276 had atrial fibrillation or atypical atrial flutter and 10 had ventricular tachycardia. Success of transseptal access and complications related to TSP were analyzed. Adverse event requiring additional intervention was defined as major complication. Results Double TSPs were performed in 253 patients and single in 104 patients. Additional ablation procedures were needed in 26 patients and the rest had a single CA procedure. Altogether, 661 TSPs (274 double and 111 single) were attempted and 659 were successful (99.7%). Both TSPs failed due to severely thickened interatrial septum after previous cardiac surgery. In 14 patients (21 TSPs, 3.2%) a cardiac implantable electronic device (CEID) was present. ICE provided excellent lead visualisation and no lead dislodgements were recorded. Additional radiofrequency energy application to the transseptal needle was used for 3 challenging TSPs. Minor complications (pericardial effusions managed conservatively) occurred after 7 double TSP procedures (12/661, 1.8%). Major complication with pericardial tamponade (requiring pericardiocentesis) occurred during one double TSP (2/661, 0.3%). No TSP-related embolic complications were observed. Conclusion ICE-guided TSP in CA of left-sided tachyarrhythmias is safe with excellent success rates. In addition, ICE could provide additional reassurance in difficult cases and in patients with CEIDs.