The coexistence of heart failure (HF) and type 2 diabetes mellitus (T2DM) is common and poses a serious threat to human health because these diseases have a high degree of commonality at the vascular level. However, the diagnosis of HF in primary care can be challenging, leading to the risk of inadequate management of both conditions. Using two case reports as examples, we attempt to shed light on the issues involved in this challenge. In the first case presentation, a 62-year-old male patient with T2DM and dyspnea was initially diagnosed with HF during primary care. However, further workup revealed that the actual cause of the patient's breathlessness was the exacerbation of chronic obstructive pulmonary disease. In the second case, a 59-year-old woman with T2DM and obesity complained of leg swelling that was attributed to chronic venous insufficiency by a primary care physician. A correct diagnosis of HF with preserved ejection fraction (HFpEF) was made using N-terminal pro-B-type natriuretic peptide and echocardiography. Due to diabetic vasculopathy HF is more likely to progress with a preserved ejection fraction. In addition, symptoms of COPD or obesity may overlap with or mask symptoms of HFpEF. The issues of over-and misdiagnosis of HFpEF in primary care are discussed in our review, which emphasizes the nonspecific nature of symptoms, such as breathlessness and leg edema in patients with type 2 diabetes mellitus. It is of utmost importance for healthcare providers to be aware of unusual manifestations of heart failure and, vice versa, of diseases that masquerade as heart failure. This will enable them to manage risks in these patients with greater consistency.