Objective: To explore whether ultrasonographic measurements of tongue thickness are associated with swallowing function and related clinical domains in patients with amyotrophic lateral sclerosis (ALS), this feasibility study was conducted. Few studies have examined the usefulness of ultrasonographic tongue thickness measurement in patients with ALS, but its association with physiological measures remains unclear. Methods: Ten patients with ALS underwent tongue thickness measurement using ultrasonography. Clinical assessments including the Korean version of the ALS Functional Rating Scale-Revised (K-ALSFRS-R), Functional Oral Intake Scale (FOIS), Eating Assessment Tool-10 (EAT-10), Dysphagia Handicap Index, Korean version of the Swallowing Quality of Life Questionnaire, Mini Nutritional Assessment–Short Form (MNA-SF), handgrip strength, and bioelectrical impedance analysis for skeletal muscle index (SMI) were performed. Swallowing physiology was evaluated using the Modified Barium Swallow Impairment Profile (MBSImP), Penetration-Aspiration Scale. Simple and partial Pearson’s correlation analyses as well as univariate regression were performed with adjustments for age, sex, and body mass index (BMI). Results: Tongue thickness showed significant associations with multiple functional and systemic measures in the unadjusted analyses, including FOIS, EAT-10, MNA-SF, BMI, SMI, K-ALSFRS-R. After adjustment, the most consistent associations were observed with the MBSImP oral, pharyngeal, and combined phase scores. Conclusion Tongue ultrasonography may serve as a radiation-free method to preliminarily assess bulbar involvement in ALS. Tongue thickness was most specifically associated with dysphagia outcomes, particularly MBSImP. Given the feasibility design and small sample size, larger longitudinal studies are warranted to confirm its clinical utility in monitoring the progression of dysphagia in patients with ALS.