Background and objective: Lower extremity amputee outcome measures assess basic mobility. The Comprehensive High-Level Activity Mobility Predictor was developed to assess high-level mobility. Validity evidence was collected in military men with traumatic lower extremity amputations. This study examines its validity in a broader population. Study design: Cross-sectional. Methods: Forty-five lower extremity amputees (Medicare Functional Classification Level K3 or K4) completed the 2-min walk test, Amputee Mobility Predictor with Prosthesis, and Comprehensive High-Level Activity Mobility Predictor. Results: The Comprehensive High-Level Activity Mobility Predictor correlated with the Amputee Mobility Predictor with Prosthesis ( r = 0.77, p < 0.01) and the 2-min walk test ( r = 0.65, p < 0.01). The Comprehensive High-Level Activity Mobility Predictor differentiated between K-levels, age groups, etiology of amputation, and amputation level ( p < 0.005). No ceiling effect was observed (range: 2.5–29/40). Conclusion: This study provides convergent and discriminative validity evidence for Comprehensive High-Level Activity Mobility Predictor use in a more heterogeneous population than previously published, suggesting that clinicians should feel confident to use it as an outcome measure for individuals with amputations who are capable of more than level-ground walking. Clinical relevance Clinically, the Comprehensive High-Level Activity Mobility Predictor has validity evidence for use in a more heterogeneous population than originally demonstrated, including civilians, women, people over age 40 years, and non-traumatic etiologies. The Comprehensive High-Level Activity Mobility Predictor may be more useful than standard outcome measures for high-level mobility.