The health costs for heart failure (HF) among individuals with and without diabetes can help understand the conjoint burden of diabetes and HF. Using the 2008–2019 US national Medical Expenditure Panel Survey data including 2,019 adults with HF and a 2-part adjusted model, we estimated mean and adjusted incremental direct medical expenditures related to diabetes. The total direct expenditures for individuals with HF increased by 27%: $24,725 (95% confidence interval [CI]: $20,457-$28,993) in 2008-2009 to $31,426 (95% CI: $25,705-$37,147) in 2018-2019. The expenditures rose by 34% among those with diabetes. Inpatient costs represented the highest fraction of costs ∼ 43.3 % and were 8% higher among those with diabetes vs. those without diabetes. The drug costs accounted for 24% of all costs, increased by 44%, and were 86% higher among HF patients with diabetes vs. those without diabetes. The adjusted excess costs among individuals with HF and diabetes vs. HF without diabetes was $6,818 (95% CI: 2,241-11,395); the corresponding excess costs for drugs and medical costs other than drugs were $3,297 (95% CI: 2,168-4,426) and $3,554 (95% CI: -777-7,886). Among US adults with HF, the estimated adjusted total direct excess costs were $5.2 billion per year higher among individuals with diabetes vs. those without diabetes. In conclusion, diabetes is associated with substantially increased health care costs among patients with HF, suggesting the need for an integrated management of diabetes and HF.