Objective. Previous studies have demonstrated that muscle ultrasound (US) can be reliably performed at the patient bedside by novice assessors with minimal training. The primary objective of this study was to determine the interrater reliability of muscle US image acquisition by physical therapists and physical therapist students. Secondarily, this study was designed to elucidate the process for training physical therapists to perform peripheral skeletal muscle US. Methods. This was a cross-sectional observational study. Four novices and 1 expert participated in the study. Novice sonographers engaged in a structured training program prior to implementation. US images were obtained on the biceps brachii, quadriceps femoris, and tibialis anterior muscles in 3 groups: patients in the intensive care unit, patients on the hospital ward, and participants in the outpatient gym who were healthy. Reliability of image acquisition was analyzed compared with the expert sonographer. Results. Intraclass correlation coefficient values ranged from 0.76 to 0.97 with an average for all raters and all muscles of 0.903, indicating excellent reliability of image acquisition. In general, the experienced physical therapist had higher or similar intraclass correlation coefficient values compared with the physical therapist students in relation to the expert sonographer. Conclusions. Excellent interrater reliability for US was observed regardless of the level of experience, severity of patient illness, or patient setting. These findings indicate that the use of muscle US by physical therapists can accurately capture reliable images in patients with a range of illness severity and different clinical practice settings across the continuum of care. Impact. Physical therapists can utilize US to obtain images to assess muscle morphology. Lay Summary. Physical therapists can use noninvasive US as an imaging tool to assess the size and quality of peripheral skeletal muscle. This study demonstrates that physical therapists can receive training to reliably obtain muscle images in patients admitted to the intensive care unit who may be at risk for muscle wasting and may benefit from early rehabilitation.