Patient-reported outcomes (PROs) can be used to evaluate perceived capacity of an individual in executing tasks in a natural environment with their prosthetic device. According to the World Health Organization International Classification of Health, Functioning, and Disability (ICF) models, there may be specific factors of a person, factors of assistive prosthetic technology, or factors related to the health condition or body function that affect their functioning and disability. However, an understanding of factors affecting an upper limb prosthesis user's perception of their ability to execute tasks in a natural environment is not well established. To use the ICF model to identify which health condition-related, body function, environmental, and personal factors influence activity as measured by perceived function in the upper limb prosthesis user population. Quantitative clinical descriptive study. Clinical offices within outpatient private practice (removed for blinding). A sample of 101 participants with upper limb amputation who use a prosthetic device and were undergoing a prosthesis fitting process. Not applicable. PROs on pain with/without a prosthesis, satisfaction, and perceived function derived from the Comprehensive Arm Prosthesis and Rehabilitation Outcomes Questionnaire. Model coefficients indicate that with a unit increase in satisfaction (p< .001) and pain (p= .031) scores (with higher pain scores signifying less pain), the mean of perceived function increases by 0.66 and 0.47 units, respectively. Conversely, for individuals with elbow disarticulation, transhumeral, shoulder disarticulation, and interscapulothoracic amputations, the mean of perceived function decreases by 22.02 units (p= .006). Based on our sample, perceived function is significantly associated with satisfaction, pain, and amputation level. These findings could potentially help to inform initial clinical approach and targeted outcomes for patients based on these factors.