Objective To investigate the effects of frailty and decreased estimated glomerular filtration rate (eGFR) on re-hospitalization in the elderly inpatients. Methods A total of 274 elderly inpatients (aged ≥65 years) admitted in our department from July 2015 to December 2016 were prospectively recruited in this study. Their status of frailty was evaluated with frailty phenotype (FP), and then they were assigned into the frail group, pre-frail group and non-frail group. Their general information and clinical data, medical history, comorbidity number, medication number and laboratory examination results were collected, and eGFR was calculated based on serum creatinine (SCr) level. The patients were also divided into eGFR >60 ml/(min·1.73 m²) group and ≤60 ml/(min·1.73 m²) group. All the patients were followed up for 1 year, and the endpoint event was re-hospitalization. SPSS statistics 18.0 was used to perform the statistical analysis. Analysis of variance or Chi-square test was employed for comparison on different data types. Cox regression analysis was adopted for the effects of frailty and decreased eGFR on re-hospitalization. ResultsOf the 274 patients, there were 76(27.7%) patients assigned into non-frail group, 114(41.6%) into pre-frail group, and 84(30.6%) into frail group. Compared with the non-frail group, the eGFR level was significantly lower (P=0.018), while the proportions of older age, hypertension, chronic obstructive pulmonary disease (COPD) and eGFR ≤60 ml/(min·1.73 m²) were obviously higher in the pre-frail and frail groups (P<0.05). What′s more, the frail group had largest numbers of comorbidities and of medications. After adjustment for age, sex and comorbidities, the patients with eGFR ≤60 ml/(min·1.73 m²) and frailty at the same time had an increased risk for re-hospitalization compared with those with eGFR >60 ml/(min·1.73 m²) and non-frailty (HR=2.40, 95%CI 1.39-4.16). Conclusion The frail elderly inpatients commonly have lower eGFR level, and those with decreased eGFR are prone to re-hospitalization.