We investigated the relationship between high carcinoembryonic antigen (CEA) levels and low skeletal muscle mass (LMM) in asymptomatic adults in a population-based study. A total of 202,602 adults (mean age 41.7 years) without malignancy, stroke, cardiovascular disease, or chronic lung/liver disease were included. A high CEA level was defined as ≥5 ng/mL. Skeletal muscle mass index (SMI) was calculated based on appendicular muscle mass (kg)/height (m)2. Participants were classified into three groups based on SMI: “normal”, “mild LMM”, and “severe LMM.” The prevalence of elevated CEA levels was the highest in subjects with severe LMM (4.2%), followed by those with mild LMM (1.6%) and normal muscle mass (1.1%) (p for trend < 0.001). In multivariate logistic regression analysis, high CEA was independently associated with having mild LMM (adjusted odds ratio, 1.139 [95% confidence interval, 1.092–1.188]) and severe LMM (2.611 [2.055–3.319]) compared to normal muscle mass. Furthermore, the association between high CEA and severe LMM was stronger in women than that in men (women, 5.373 [2.705–10.669]; men, 2.273 [1.762–2.933]). Elevated CEA levels were significantly associated with a higher prevalence of LMM. Therefore, increased CEA could be used as a biomarker for detecting LMM in adults without cancer.