Background- Cobblestone production is highly labor intensive and physically demanding work that exposes workers for musculoskeletal disorders. Evidences on measuring exposure level are limited in this area. As a result studying the magnitude and factors incorporating the ergonomic hazard exposure level measurement is crucial. Objective- The main objective of the study is to assess the prevalence and associated factors of work related musculoskeletal disorders among cobble stone workers. Methods- Cross-sectional study was conducted from December 2016-June 2017 among cobble stone workers in Addis Ababa with a sample size of 537 using Nordic muscoloskletal disorder assessmet questionnaire and 56 paicipants using quick exposure cheek ergonomic hazard assessment tool. The data were collected by interviewing participants by trained six data collectors and three supervisors. The data were entered and cleaned using epi info version 7 and imported to statistical package for social science software version 20 for analysis. The data were analyzed using descriptive statistical method for magnitude and using bivariate and multivariable logistic regression models to identify factors associatiated with work related musculoskeletal disorder. Results- A total of 512 respondents included in this study, with 95% response rate.Over all 12 month prevalence 417(81.4%) of work related musculoskkletal disorder were obtained. From different body parts lower back is 65.5%, wrist 51.6%, shoulder 47.9% and neck 24.2% were found. Job stress (OR=1.75), working days (OR=3.38), awkward working posture (OR=3.29), lack of break time (OR=2.2) and ergonomic training (OR=2.9) found to be have statistically significant association with work related musculoskeltal disorder.The result obtained from quick exposure cheek reveals that exposure level of very high for back,high and very high for shoulder and wrist and moderate for neck. Conclusion and recommendation- Work related musculoskletal disorder among cobblestone workers are characterized with very high prevalence with high and very high ergonomic hazard exposure level for majority of body parts. Work load, twisting bending position, lack of break and lack of ergonomic training are factors for the development of work related musculoskletal disorders therefore ergonomic training mainly focusing on manual handling should be provided.