The incidence of acute pyelonephritis (APN) in the diabetic population is comparatively higher and tends to be more complicated, with serious outcomes. Although complicated pyelonephritis (PN) needs hospital admission and intravenous antibiotics, the magnitude of hospital stay due to comorbidities is limited. This study's aim was to assess the impact of diabetes mellitus on length of hospital stay among patients with PN. Methods We did a retrospective data review of 520 randomly selected hospitalized patients of PN from March 2015 to December 2019 from a tertiary care center. Electronic medical records were used for identifying medical conditions through ICD-10 coding. Length of stay (LOS) was categorized as < five days and ≥ five days. Chisquared tests were used to compare categorical parameters. Logistic regression models were used for multivariate analyses. Results The study included 520 patients with PN; 194 (37.3 %) men and 326 (62.7%) women. Overall, there were 353 (67.8 %) and 167 (32.1 %) patients with LOS < five and ≥ five days respectively. Most of the patients had lower urinary tract symptoms (90%); among them, the majority (92%) were discharged within five days. Likewise, half of the patients had diabetes (51.2); among them, 53% were discharged after five days. Older age (