Background: Presence of myocardial fibrosis in well-established non-ischaemic dilated cardiomyopathy (NIDCM) is associated with adverse clinical outcomes. However, the impact of myocardial fibrosis at first presentation in NIDCM, and its long-term association with left ventricular (LV) dysfunction, heart failure (HF) and ventricular arrhythmia (VA) remains unclear. We investigated whether the presence of myocardial fibrosis quantified by late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) at presentation, is independently associated with long-term major adverse cardiovascular events (MACE) in patients with first presentation NIDCM. Methods: Consecutive patients with a first diagnosis of NIDCM were recruited. Patients underwent LGE-CMR at baseline. Replacement myocardial fibrosis by LGE-CMR was quantified by experienced observers blinded to patient outcome. MACE was defined as a composite end-point including cardiac death, HF rehospitalisation and the occurrence of sustained VA. Results: Fifty-one patients with first presentation NIDCM were included, of which 49 (96%) had follow up and outcome data. Median follow up was 8.2 years. Both the LGE positive and LGE negative groups had similar clinical characteristics at follow up. In univariate Cox regression analysis, positive LGE was associated with MACE (HR:3.44; 95% CI:1.89 to 6.24, p-value < 0.001) and HF rehospitalisation (HR:2.89; 95% CI:1.42 to 5.85, p-value = 0.003). In multivariate Cox regression, positive LGE-CMR was independently associated with MACE (HR:3.53; 95% CI:1.51 to 8.27, p-value = 0.004) and HF rehospitalisation (HR:3.07; 95% CI:1.24 to 7.59, p-value = 0.015). Conclusions: The presence of myocardial fibrosis in first presentation NIDCM is independently associated with an increased risk of HF rehospitalisation, at long term follow-up.