Background: Several studies have associated a large breast size with an increased prevalence and severity of musculoskeletal pain, particularly pain in the upper torso. Despite this evidence, no research has explored whether breast size or related characteristics are risk factors for upper torso musculoskeletal pain. Methods: A backward multiple regression analysis was performed to identify whether characteristics of the breasts and upper torso, as well as physical factors known to be associated with musculoskeletal pain, could predict musculoskeletal pain among a cohort of 378 Australian women aged 18 years and over who had a wide range of breast sizes. Findings: The model identified that breast volume, age and nipple-to-nipple distance predicted 23% of the variance in upper torso musculoskeletal pain reported by the participants. Interpretation: Women with a larger breast volume, lower age and a greater nipple-to-nipple distance were predicted to report a higher upper torso musculoskeletal pain score.