IntroductionThe length of stay (LOS) in hospitals is a widely used and important criteria for evaluating hospital performance. The aim of this study was to determine factors affecting LOS in teaching hospitals of Qazvin Providence.MethodsIn this cross-sectional study, patients’ health records were randomly selected from archives in teaching hospitals of Qazvin in 2013. Data were collected through a data entry form and were analyzed using Kolmogorov–Smirnov, Kruskal–Wallis, and Mann–Whitney U tests at the significant level of 0.05.ResultsThe mean of hospital LOS was 5.45 ± 6.14 days. Age, employment, marital status, history of previous admission, patient condition at discharge, method of payment, and type of treatment had an impact on LOS (p<0.05). Other factors, including gender, place of residence, and type of admission, did not affect LOS.ConclusionBecause hospitals consume a perceptible part of resources in a health system, controlled and optimized use of its resources help to save a lot. Therefore, this study showed many clinical and nonclinical factors affect LOS in evaluating these factors, which may reduce inappropriate hospital stays and decrease costs.