Cardiovascular disease is a negative health outcome of obstructive sleep apnea (OSA). Risk factors associated with OSA development include low physical activity (PA), high body mass index (BMI), and increasing age (>50 years), and weight loss is usually recommended as treatment. This cross-sectional study examined the association between PA, BMI, and OSA severity in manual workers. Fifty-five participants (23 females and 32 males; mean age 55.2 years), were examined for OSA and completed a PA and anthropometric assessment. On average, OSA severity was mild, PA levels were moderate, and 32% of the sample was classified as obese. PA was negatively associated with OSA severity, but BMI strongly independently predicted OSA severity, with no evidence of mediation. As both PA and BMI were significantly associated with OSA in older manual workers, increasing PA should also be a focus of treatment for OSA.