According to the 2017 Global Burden of Disease study, low back pain (LBP) was ranked first among health issues in terms of years lived with disability (YLDs) [1]. It is also the second highest cause of YLDs among 15-19-year-old, accounting for more YLDs than other health problems, such as asthma, alcohol consumption, drug use, and road traffic injury [2]. LBP is a prevalent condition among school-age students, but it has not received sufficient attention [3]. In developing countries such as Thailand, Zimbabwe, and Bosnia and Herzegovina, it was reported that OBJECTIVES: This study investigated the prevalence of low back pain (LBP) and its risk factors among elementary-school students. METHODS: In this cross-sectional study, 693 elementary students from Hamadan city, western Iran, were selected by multistage stratified cluster sampling. Data were collected through interviews using questionnaires. Posture and psychosocial elements were assessed using the observational Rapid Upper Limb Assessment (RULA) checklist and the standard Strengths and Difficulties Questionnaire, respectively. Penalized logistic regression with the group smoothly-clipped absolute deviation regularization method was used for variable selection and data analysis (α=0.05). The chi-square test was also used. RESULTS: In total, 26.6% of the students (7-12 years old) reported LBP in the last month. Older age (odds ratio [OR], 3.08; 95% confidence interval [CI], 1.80 to 5.26), watching TV for more than 3 hours a day (