Aim: It is unknown whether safety and clinical endpoints by use of sacubitril/valsartan (an angiotensin receptor–neprilysin inhibitor [ARNI]) are affected by mineralocorticoid receptor antagonists (MRA) in high-risk myocardial infarction (MI) patients. The aim of this study was to examine whether MRA modifies safety and clinical endpoints by use of sacubitril/valsartan in patients with a MI and left ventricular systolic dysfunction (LVSD) and/or pulmonary congestion. Methods and results: Patients (n = 5661) included in the PARADISE MI trial (Prospective ARNI vs. ACE Inhibitor Trial to Determine Superiority in Reducing Heart Failure Events After MI) were stratified according to MRA. Primary outcomes in this substudy were worsening heart failure or cardiovascular death. Safety was defined as symptomatic hypotension, hyperkalaemia >5.5 mmol/L, or permanent drug discontinuation. A total of 2338 patients (41%) were treated with MRA. Safety of ARNI compared to ramipril was not altered significantly by ± MRA, and both groups had similar increase in symptomatic hypotension with ARNI. In patients taking MRA, the risk of hyperkalaemia or permanent drug discontinuation was not significantly altered by ARNI (p > 0.05 for all comparisons). The effect of ARNI compared with ramipril was similar in those who were and were not taking MRA (hazard ratio [HR]_MRA 0.96, 95% confidence interval [CI] 0.77–1.19 and HR_MRA– 0.87, 95% CI 0.71–1.05, for the primary endpoint; p = 0.51 for interaction [Clinical Endpoint Committee adjudicated]); similar findings were observed if investigator-reported endpoints were evaluated (p = 0.61 for interaction). Conclusions: Use of a MRA did not modify safety or clinical endpoints related to initiation of ARNI compared to ramipril in the post-MI setting in patients with LVSD and/or congestion.