Background Left ventricular (LV) involvement is frequently observed in arrhythmogenic cardiomyopathy (ACM). We investigated the association of LV myocardial assessment using cardiac magnetic resonance (CMR) with clinical outcomes including heart failure (HF)‐related events in ACM. Methods and Results We retrospectively analyzed 60 patients with ACM between 2005 and 2020 according to the 2010 Task Force Criteria and assessed HF‐related events (HF hospitalization, heart transplantation, and cardiac death) and ventricular tachycardia events. We analyzed CMR findings including late gadolinium enhancement (LGE) in all subjects and obtained mapping values (native T1, extracellular volume, and T2) on 30 (50%) patients out of them. Among the study population (mean age 49 years, 77% male), 41 (68%) patients had LV LGE. During a median follow‐up of 34 months, there were 13 (22%) HF‐related events, and 20 (30%) ventricular tachycardia events. Kaplan‐Meier survival analysis revealed that HF‐related events occurred only in patients with LV LGE (+) (versus LV LGE (‐), log‐rank P =0.006), and the events were not significantly different regarding right ventricular LGE (log‐rank P >0.999). When categorized by median value for each mapping parameter, HF‐related events occurred more in patients with higher native T1 (versus lower native T1, log‐rank P =0.002), and higher T2 (versus lower T2, log‐rank P =0.002), higher extracellular volume (versus lower extracellular volume, log‐rank P =0.002). However, regarding ventricular tachycardia events, there were no significant differences according to these CMR markers. Conclusions LV myocardial assessment using CMR with LGE imaging and native T1, T2, and extracellular volume markers were significantly associated with HF‐related event risk in patients with ACM.