The purpose of this study was to test the reliability of the Activity Measure for Post-Acute Care (AM-PAC) "6-Clicks" mobility and activity short forms between patients and therapist proxies. As a secondary aim, reliability was examined when patients completed their self-report before versus after the therapist evaluation. Patients being seen for an initial physical therapist (N = 70) or occupational therapist (N = 71) evaluation in the acute care hospital completed the "6-Clicks" mobility short form (if a physical therapist evaluation) or activity short form (if an occupational therapist evaluation). Whether patients completed their self-assessment before or after the evaluation was randomized. Patient- and therapist-rated "6-Clicks" raw scores were converted to AM-PAC T-scores for comparison. Reliability was assessed with intraclass correlation coefficients (ICCs) and Bland-Altman plots, and agreement was assessed with weighted kappa values. The ICCs for the "6-Clicks" mobility and daily activity short forms were 0.57 (95% CI = 0.42-0.69) and 0.45 (95% CI = 0.28-0.59), respectively. For both short forms, reliability was higher when the patient completed the self-assessment after versus before the therapist evaluation (ICC = 0.67, 95% CI = 0.47-0.80 vs ICC = 0.50, 95% CI = 0.26-0.67 for the mobility short form; and ICC = 0.52, 95% CI = 0.29-0.70 vs ICC = 0.34, 95% CI = 0.06-0.56 for the activity short form). Reliability of the "6-Clicks" total scores was moderate for both the mobility and activity short forms, though higher for the mobility short form and when patients' self-report occurred after the therapist evaluation. Reliability of the AM-PAC "6-Clicks" short forms is moderate when comparing scores from patients with those of therapists responding as proxies. The short forms are useful for measuring participants' function in the acute care hospital; however, it is critical to recognize limitations in reliability between clinician- and patient-reported AM-PAC scores when evaluating longitudinal change and recovery.