Heart failure with reduced ejection fraction (HFrEF) is an increasing global pandemic affecting more than 30 million individuals worldwide. Importantly, HFrEF is frequently accompanied by the presence of cardiac and non-cardiac comorbidities that may greatly influence the management and prognosis of the disease. In this review article, we will focus on three important comorbidities in HFrEF; atrial fibrillation (AF), advanced renal disease, and elderly, which all have a paramount impact on progression of the disease, management strategies, and response to therapy. AF is very common in HFrEF and shares many risk factors. AF aggravates heart failure and contributes to HF-related adverse clinical outcomes; hence it requires special consideration in HFrEF management. The kidney function is largely affected by the reduced cardiac output developed in the setting of HFrEF, and the neurohormonal feedback effects create a complex interplay that pose challenges in the management of HFrEF when renal function is significantly impaired. Cardiorenal syndrome is a challenging sequela with increased morbidity and mortality thereby reflecting the delicate and complex balance between the heart and the kidney in HFrEF and renal failure conditions. Furthermore, patients with advanced renal failure have poor prognosis in the presence of HFrEF with limited treatment options. Finally, aging and frailty are important factors that influence treatment strategies in HFrEF with greater emphasis on tolerability and safety of the various HFrEF therapies in elderly individuals.