Background: Musculoskeletal pain (MSP) is common among lactating mothers. The aims of this study were to assess the prevalence of MSP and its association with the positioning of lactating mothers in Riyadh, Saudi Arabia. Methods: This was a descriptive cross-sectional survey study using an online self-administered questionnaire. Results: 336 women aged 20–50 years participated in this study (58.3% reported vaginal delivery, 74.1% had one to four children, 61.3% had a bachelor’s degree or higher, and 45.5% worked). Only 25% of the mothers were given health education regarding MSP. 97.3% of mothers reported pain on at least one part of their body. There were differences in pain intensity ratings across different locations (with a median and interquartile range in parentheses): lower backs at 0 (0, 6) and upper backs at 2 (0, 5), necks at 3 (0, 6), shoulders at 3 (0, 5) and arms at 2 (0, 4), and hands at 1 (0, 4). MSP prevalence ranges from 58.6% for arm and hand to 72.3% and 67.6% for lower back and neck, respectively. MSP prevalence is significantly associated with breastfeeding positions (p 0.001). A cradle position was the most commonly used (54.8%), and it was associated with MSP across different locations (p 0.001). Conclusions: The prevalence of lower back and neck pain is higher among breastfeeding mothers in Riyadh, Saudi Arabia. MSP and breastfeeding position were significantly associated. Mothers received limited health education about MSP.