Background: There is limited data on the safety and efficacy of a novel high-definition mapping catheter with 16 equidistant electrodes (Advisor HD Grid). We describe procedural details for the treatment of complex atrial arrhythmias and associated outcomes using this novel catheter design. Methods and Results: The HD Grid was employed for patients with clinically relevant arrhythmia using the EnSite Precision™ electroanatomic mapping system. AVRT and typical flutter cases were excluded. Major procedural complications were defined as bleeding, stroke or TIA, sepsis, and death from any cause, whereas minor complications were defined as no changes to the length of hospital stay or to the expected management of the patient. Recurrence was defined as sustained tachycardia after 3 months post-procedure. Consecutive patients attending for the treatment of paroxysmal atrial fibrillation (66), persistent atrial fibrillation (38), atrial tachycardia (29), and atypical flutter (18) were included, resulting in a final inclusion of 142 patients and 151 procedures. Eighty-four patients (55.3%) received general anesthetic and intracardiac echocardiography was used in 23 (15.1%). Long term follow-up was available in 150/151 procedures, mean 185.2±134.3 days; 32 patients (21.3%) documented recurrence. Three (2.0%) patients experienced complications within 30-days of the procedure including acute tamponade (1), TIA (1) and stroke (1) and 1 (0.7%) died from complications of septic arthritis 183 days post-procedure. Conclusion: The novel HD Grid differs significantly in design and handling compared to the traditional multielectrode catheters. Our data report procedural outcomes in line with contemporary clinical expectations with low complication and recurrence rates.