Objectives: Limited studies have been performed to assess readmission following hospitalization for community-onset pneumonia in an Asian population. We evaluated the rates, reasons, and risk factors for 30 day readmission following hospitalization for community-onset pneumonia (COP) in the general adult population of Korea.Methods: We performed a retrospective observational study of 1,021 patients with COP. The primary end point was all-cause hospital readmission within 30 days following discharge after the initial hospitalization. Hospital readmission was classified as (1) pneumonia-related or (2) pneumonia-unrelated readmission.Results: During the study period, 1,021 patients were eligible for inclusion. Of the 862 patients who survived to hospital discharge, 72 (8.4%) were rehospitalized within 30 days. In the multivariable analysis, pneumonia related readmission was associated with para/hemiplegia, malignancy, pneumonia severity index (PSI) class ≥ 4 and clinical instability ≥ 1 at hospital discharge. Chronic lung disease, chronic kidney disease, treatment failure, and decompensation of comorbidities were associated with the pneumonia-unrelated 30-day readmission rate.Conclusions: Rehospitalizations within 30 days following discharge were frequent among patients with COP. The risk factors for pneumonia-related and -unrelated readmission were different. Aspiration prevention, discharge at the optimal time, and close monitoring of comorbidities may reduce the frequency of readmission among patients with COP.