Heart failure (HF), especially HF with reduced ejection fraction (HFrEF), presents complex challenges, particularly in the aging population where it often coexists with type 2 diabetes mellitus (T2DM). To analyze the effect of dapagliflozin treatment on cardiac, renal function, and safety in patients with HFrEF combined with T2DM. Patients with T2DM complicated with HFrEF who underwent treatment in our hospital from February 2018 to March 2023 were retrospectively analyzed as the subjects of this study. The propensity score matching method was used, and a total of 102 eligible samples were scaled. The clinical efficacy of the two groups was evaluated at the end of the treatment, comparing the results of blood glucose, insulin, cardiac function, markers of myocardial injury, renal function indexes, and 6-min walk test (6MWT) before and after the treatment. We compared the occurrence of adverse effects on the treatment process of the two groups of patients. The incidence of adverse outcomes in patients within six months of treatment was counted. The overall clinical efficacy rate of patients in the study group was significantly higher than that of patients in the control group (P = 0.013). After treatment, the pancreatic beta-cell function index, left ventricular ejection fraction, and glomerular filtration rate of patients in the study group were significantly higher than control group (P < 0.001), while their fasting plasma glucose, 2-h postprandial glucose, glycosylated hemoglobin, insulin resistance index, left ventricular end-systolic diameter, left ventricular end-diastolic diameter, cardiac troponin I, creatine kinase-MB, N-terminal pro b-type natriuretic peptide, serum creatinine, and blood urea nitrogen were significantly lower than those of the control group. After treatment, patients in the study group had a significantly higher 6MWT than those in the control group (P < 0.001). Hypoglycemic reaction (P = 0.647), urinary tract infection (P = 0.558), gastrointestinal adverse effect (P = 0.307), respiratory disturbance (P = 0.558), and angioedema (P = 0.647) were not statistically different. There was no significant difference between the incidence of adverse outcomes between the two groups (P = 0.250). Dapagliflozin significantly enhances clinical efficacy, cardiac and renal function, and ambulatory capacity in patients with HFrEF and T2DM without an increased risk of adverse effects or outcomes.