Mounting evidence suggests that cognitive impairment is strongly associated with disability in activities of daily living (ADL disability) and long-term care (LTC) costs. However, studies forecasting future LTC costs often overlook these relationships. Consequently, this study aims to more accurately project future LTC costs in China over the next 20 years by considering the intertwined association between disability and cognitive impairment on future LTC costs. Data were from 10 959 adults ≥65 years from the 2005-2018 waves of the Chinese Longitudinal Healthy Longevity Surveys. We used the Markov model to project the population of China and track the transition of older adults in the next 20 years between 4 disability-cognition states. We employed a 2-part model to estimate LTC costs (direct and indirect LTC costs) per capita. The proportion of disabled older adults with cognitive impairment was projected to increase from 1.4% in 2021 to 3.4% in 2040, while that of those without cognitive impairment was projected to decrease from 4.7% in 2021 to 4.5% in 2040. The direct and indirect LTC costs were projected to increase from 0.3% and 0.2% of gross domestic product (GDP) in 2021 to 1.4% and 0.7% in 2040 for disabled persons without cognitive impairment and from 0.1% and 0.1% of GDP in 2021 to 1.3% and 1.3% in 2040 for those with cognitive impairment, respectively. Policy-makers could include the assessment of cognition in the LTC needs assessment and allocate more compensation to LTC insurance participants with cognitive impairment.