Introduction: The benefits of an implantable cardioverter-defibrillator (ICD) in significantly reducing sudden cardiac death in ischaemic (ICM) and non-ischaemic cardiomyopathy (NICM) patients has been well demonstrated. Our study investigated the characteristics of ventricular tachycardias (VT) between ICM and NICM patients who received ICD therapy. Methods: Between August 2015 and August 2017, 58 patients (male = 50; age = 66 ± 16 years; ICM = 26, NICM = 32) presented with ICD device therapy (anti-tachycardia pacing (ATP) or shock). Cycle length of the tachyarrhythmia (TCL) and time from implant to first presentation were analysed, as were VT/VF occurrences and electrical storm events. Results: 152 patients had ICD implanted (74 NICM, 78 ICM). Ejection fraction and duration of follow up in both groups was similar. 32 presented with therapy (17 ATP, 15 Shock) in NICM and 26 in ICM. 4 in ICM and 4 in NICM presented with VT storm. TCL was significantly faster in NICM patients versus ICM patients (272 ± 48 ms vs. 307 ± 47 ms; p = 0.01). There was no significant difference in time from implant to first presentation (27 ± 24 months vs. 25 ± 25 months; p = 0.83). Conclusion: NICM and ICM patients had the same rate of ICD therapy for primary prevention of SCD. NICM patients had a faster TCL compared to ICM patients. There was no difference between groups in terms of time from implant to first presentation. These findings have implications for the approach to catheter ablation and appropriate programming of ICD therapies.