Objective: The purpose of this study was to clarify the relationship between respiratory muscle strength and skeletal muscle mass (trunk, upper limbs, and lower limbs) in older people who were certified as requiring nursing or supportive care. Methods: Thirty-five older people (65 years or older) who were certified as requiring nursing care or support were included in the study. The subjects were divided into a non-sarcopenic group (n = 12) and a sarcopenic group (n = 23) according to the sarcopenia diagnostic criteria proposed by the Asian Working Group for Sarcopenia. Maximum inspiratory pressure, maximum expiratory pressure, skeletal muscle mass (trunk, upper and lower limbs), and hand grip strength were measured. Pearson’s correlation coefficient and multiple regression analysis were used for statistical processing. Results: In the non-sarcopenic group, both expiratory muscle strength and hand grip strength were correlated with skeletal muscle mass. In the sarcopenia group, expiratory muscle strength was not correlated with skeletal muscle mass, and only hand grip strength was correlated with upper limb muscle mass. Multiple regression analysis revealed that, in the non-sarcopenic group, trunk muscle mass was the primary factor in expiratory muscle strength and upper limb muscle mass was the primary factor in hand grip strength. In the sarcopenia group, upper limb muscle mass was found to be the main factor in hand grip strength. Conclusion: Our results highlight the importance of assessing expiratory muscle strength and trunk muscle mass before sarcopenia develops in older people who require support and nursing care.