Shifts in epidemiological patterns foretell a rapid increase in the number of patients with heart failure (HF) globally, representing a significant health and economic burden. Heart failure with preserved ejection (HFpEF) is now considered the prevailing subtype of HF, with no effective treatment available to combat this syndrome. Previous studies have highlighted the cardioprotective role of MKK7 during cardiac pathology, however, no extensive research has been performed to examine MKK7 in the context of HFpEF. This study aimed to address this shortcoming by using adeno-associated virus (AAV) 9 to overexpress MKK7 in the two-hit clinically relevant HFpEF mouse model. We report that cardiomyocyte-specific overexpression of MKK7 improved the HFpEF phenotype in mice, by impeding cardiac diastolic dysfunction and myocardial fibrosis. Mechanistically, it was found that MKK7 ameliorated ER stress by maintaining IRE1-XBP1 signalling and blunted CHOP increase in the myocardium. To summarise, MKK7 overexpression holds the ability to protect the myocardium from HFpEF associated pathologies.