Abstract The paper aims to analyze the hospital inpatient care use and medical fee of people with ID co-occurring with schizophrenia in Taiwan. A nationwide data were collected concerning hospital admission and medical expenditure of people with ID ( n = 2565) among national health insurance beneficiaries in Taiwan. Multiple regression analyses were undertaken to determine the role of the explanatory variables to hospital psychiatric inpatient care and medical expenditure. We found that there were 2565 individuals with ID used hospital psychiatric inpatient care among people with ID in 2005, and 686 cases (26.7%) co-occurring with schizophrenia according to hospital discharge claims. Those ID patients co-occurring with schizophrenia consumed more annual inpatient fee than those without schizophrenia (251,346 vs. 126,666 NTD) ( p < 0.001). We found factors of female cases, longer hospital stay in chronic ward and general ward users among ID patients co-occurring with schizophrenia used more hospital inpatient care ( R 2 = 0.417). Annual hospital inpatient days were significantly affected by factors of severe illness card holder, annual inpatient care fee, longer hospital stay in acute or chronic ward ( R 2 = 0.746). Those factors of female cases, high inpatient care users, longer hospital stay in acute ward and general ward were consuming more medical care fee than their counterparts ( R 2 = 0.620). The study highlights the future study should examine the efficacy of hospital inpatient care for people with ID and schizophrenia.