Objectives: To investigate the relationship between leg skeletal muscle mass asymmetry and usual gait speed in older adults. Methods: The subjects were 139 community-dwelling older adults. The asymmetry index was calculated using the leg skeletal muscle mass index (LSMI) values of both legs. The subjects were divided into “large” and “small” asymmetry groups based on the asymmetry index. The relationship between asymmetry and gait speed was analyzed using a linear regression model. The appendicular skeletal muscle mass index and LSMI were included as adjustment variables in the analysis. Results: The asymmetry index and having a “large” asymmetry were independently related to gait speed, even after adjusting for covariates such as appendicular skeletal muscle mass index and LSMI. Discussion: Leg skeletal muscle mass asymmetry was related to gait speed independently of the appendicular skeletal muscle mass index and LSMI values. A skeletal muscle mass evaluation among older adults should include an assessment of the total skeletal muscle mass and its asymmetry.