Objectives: To establish the inter-rater reliability of the Acute Care Index of Function (ACIF) in intensive care unit (ICU) patients and determine whether ACIF scores have predictive utility beyond ICU discharge. Background: Accurate and reliable measures of physical function are required to describe the recovery trajectory of ICU survivors. The clinimetric properties of the ACIF are yet to be established in ICU patients. Methods: Prospective observational study in a single tertiary ICU. ACIF scores were recorded independently by 2 physiotherapists across a convenience sample of 100 physiotherapy assessments, and at ICU discharge. Results: Inter-rater reliability of total ACIF scores was very strong (ICC ¼ 0.94). ACIF <0.40 at ICU discharge predicted hospital discharge to a destination other than home (area under ROC ¼ 0.79, 95% CI 0.64e0.89) (sensitivity 0.78). Conclusion: The ACIF has excellent inter-rater reliability in ICU patients and scores at ICU discharge predict the likelihood of discharge home.