BackgroundThe growing trend of ageing population has become a worldwide concern. In comparison with the youth, older people are more likely to suffer from multimorbidity and polypharmacy, both of which are associated with adverse outcomes and increased healthcare costs. This study aimed to investigate the status of multimorbidity and polypharmacy in a large sample of hospitalized older patients aged 60 years and over.MethodsA retrospective cross-sectional study was conducted among 46,799 eligible patients aged 60 years and over, who were hospitalized from January 1, 2021 to December 31, 2021. Multimorbidity was defined as the presence of 2 or more morbidities in one patient during the stay in hospital, and polypharmacy as prescription of 5 or more different oral medications. Spearman rank correlation analysis was used to assess the relationship of factors with the number of morbidities or oral medications. Odds ratio (OR) and 95% confidence interval (95% CI) were estimated from logistic regression models to determine the predictors for polypharmacy and all-cause death.ResultsThe prevalence of multimorbidity was 91.07% and increased with age. The prevalence of polypharmacy was 56.32%. Older age, polypharmacy, prolonged length of stay (LOS), higher cost on medications were significantly associated with an increased number of morbidities (all P < 0.01). The number of morbidities (OR = 1.29, 95% CI: 1.208–1.229) and LOS (OR = 1.171, 95% CI: 1.166–1.177) were potential risk factors for polypharmacy. As for all-cause death, age (OR = 1.107, 95% CI: 1.092–1.122), number of morbidities (OR = 1.495, 95% CI: 1.435–1.558) and LOS (OR = 1.020, 95% CI: 1.013–1.027) were the potential risk factors, but the number of medications (OR = 0.930, 95% CI: 0.907–0.952) and polypharmacy (OR = 0.764, 95% CI: 0.608–0.960) were associated with a reduction of mortality.ConclusionMorbidities and LOS might be predictors for polypharmacy and all-cause death. The number of oral medications was inversely associated with the risk of all-cause mortality. Appropriate polypharmacy was beneficial for the clinical outcomes of older patients during hospitalization.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12877-023-04109-4.