Low Back Pain (LBP) is an occupational disease that is often the main cause of disability, thus affecting the work and general welfare of LBP sufferers. The objective of the present study is to determine the correlation between length of work and work posture with complaints of LBP among back-office employees at X Hospital. The design of this study was a descriptive analysis, with cross-sectional study design, by total sampling technique for 44 back-office employees. Work posture risk assessment uses the Ovako Working posture Assessment System (OWAS) method and LBP complaints are measured using the Modified Oswestry Low Back Pain Disability Questionnaire. Most respondents experienced LBP complaints in the moderate disability category, and 40 people (90, 9%) needed to improve their work posture. Spearman correlation statistical test results showed there was a relationship between age (p-value= 0,000), the length of work (p-value= 0,000), work posture (p-value= 0,009) with LBP complaints on back-office employees. Providing work facilities with ergonomic chairs and tables position and doing stretching in between work hours can reduce LBP complaints.