Background: Nurses are exposed to some work-related activities and body positions that affect their musculoskeletal system and predispose them to pain, particularly in the shoulder and back regions. Low back troubles (LBT) affect the quality of life and have grave effects on economics and work because of sick leave and absenteeism. Objective: The aim of this study was to estimate the prevalence of low back pain and to assess the risk factors associated with it among nurses working in tertiary hospital in Dhahran in the Eastern Province in Saudi Arabia. Methods: Nurses working in a tertiary hospital in Dhahran were asked to fill in a self-administered questionnaire that included a section of LBT adapted from the previously validated and modified version of the Standardized Nordic Questionnaire of Musculoskeletal Symptoms. Results: The prevalence of LBT was 74.1% and out of the respondents 44.3% had an attack during the last week. Multivariate analysis revealed that risk factors significantly associated with LBT were moving wheelchair, bending and standing (increasing the risk), longer breaks, trolley moving, positioning patients, moving beds, and longer sitting time (decreasing the risk). Conclusion: LBT was highly prevalent among nurses, irrespective of their age, body mass index, department and work experience. Risk factors included short breaks and sitting time, long standing times, and some work activities (wheelchair, trolley or bed moving, positioning patients). We recommend that hospital administrations arrange proper rest periods for at-risk staff. Also, nurses should be educated about proper body mechanics when lifting heavy objects.