BackgroundProviding equitable access to health care for all populations is an important sustainable development goal. China has made significant progress in achieving equity in healthcare utilization. However, research on equity in healthcare utilization in Tibet is sparse. This study aims to evaluate changes in income-related inequity in inpatient care utilization and unmet needs between 2013 and 2018 among the Tibetan population and identify the inequity source.MethodsData for this cross-sectional study were obtained from the fifth and sixth waves of the National Health Services Survey in 2013 and 2018. After excluding observations with missing values for key variables, 11,092 and 10,397 respondents were included in this study, respectively. The outcome variables of interest were inpatient service utilization and unmet hospitalization needs. The concentration index and horizontal inequity index (HI) were used to assess income-related inequity. Non-linear decompositions were performed to identify the main contributors to inequity. In the decomposition method, need variables included sex, age, chronic diseases, and the EuroQol-Visual Analog Scale; non-need variables consisted of income, education, employment status, marital status, and health insurance schemes.ResultsThe probability of inpatient care utilization increased from 6.40% in 2013 to 8.50% in 2018. The HI for inpatient care utilization was 0.19 (P< 0.001) in 2013, whereas it decreased to 0.07 (P< 0.001) in 2018. The contribution of income to inequity in inpatient care utilization decreased from 87.09% in 2013 to 59.79% in 2018. As for unmet inpatient care needs, although its probability increased from 0.76 to 1.48%, the percentage of reasons for financial hardship decreased from 47.62 to 28.57%. The HI for unmet hospitalization need was − 0.07 in 2013 and − 0.05 in 2018, and neither was statistically significant. The New Rural Cooperative Medical Scheme made majority contributions to promote equity in unmet hospitalization need. Moreover, the female respondents reporting low EuroQol-Visual Analog Scale scores and patients with chronic disease were not only more likely to seek for inpatient care, but also have more unmet need than the reference groups.ConclusionsThe inequity in inpatient care utilization in Tibet narrowed from 2013 to 2018, and there was no inequity in unmet hospitalization needs in 2013 and 2018. Income and the New Rural Cooperative Medical Scheme are the main drivers of equity promotion. To promote access to inpatient care utilization and decrease the probability of unmet hospitalization need in future, policymakers should target high-need residents in Tibet to improve accessibility, availability, and acceptability.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12939-023-01889-4.