[Purpose] To confirm the reliability and validity of the acromion-greater tuberosity (AGT) distance measured using ultrasound and to investigate its relationship with functional impairments inpatients with stroke. [Participants and Methods] Twenty-four patients with stroke admitted between May and September 2024 were evaluated. Physical function assessments included motor paralysis, spasticity, pain (numerical rating scale [NRS]), shoulder range of motion (ROM), sensory impairments, and shoulder subluxation using the fingerbreadth palpation method. Ultrasound was used to measure the AGT distance and the thickness of the long head of the biceps tendon. [Results] A significant correlation was found between the AGT distance and subluxation, measured using the fingerbreadth palpation method, confirming its validity. The AGT distance was positively correlated with spasticity, tendon thickness, and NRS during movement but negatively correlated with motor paralysis and shoulder ROM. These findings suggest that an increased AGT distance may be associated with severity of subluxation, reduced motor function, and a higher pain level during movement. [Conclusion] The AGT distance measured using ultrasound is a valid tool for assessing shoulder subluxation and related impairments in patients with stroke. Further studies are required to explore the causal relationship between pain and tendon inflammation to guidebetter clinical management strategies.