Quality improvement initiatives in intensive care units (ICUs) have increased survival rates. Changes in functional status following ICU care have been studied, but results are inconclusive because of insufficient consideration of the combinations of critical care procedures used. Using the Japanese administrative database including the Barthel Index (BI) at admission and discharge, we measured the changes in functional status among the adult patients and determined whether longer ICU stay or use of various critical care procedures was associated with functional deterioration. Of the 12 502 528 patients admitted to 1206 hospitals over 5 consecutive years from 2006, we analyzed data from patients aged 15 years or older who survived ICU admission in 320 hospitals. Critical care procedures evaluated were ventilation, blood purification (hemodialysis, hemodiafiltration, or hemadsorption), and cardiac support devices (intra-aortic balloon pump or percutaneous cardiopulmonary support system). Functional outcomes were determined by the difference between BI at admission and at discharge and were divided into improvement, no change, or deterioration. We compared patient characteristics, principal diagnosis, comorbidities, timing of surgical procedure, complications, days in ICU, and use of critical care procedures among the 3 categories. Associations between critical care procedures and functional deterioration were identified using multivariate analysis. Of 234 209 patients with complete BI information, 7137 (3.1%) received blood purification, 27 100 (11.7%) received ventilation, 2888 (1.2%) received blood purification and ventilation, 5613 (2.4%) received a cardiac support device, 247 (0.1%) received a cardiac support device and blood purification, 10 444 (4.5%) received a cardiac support device and ventilation, and 1110 (0.5%) received a cardiac support device, ventilation, and blood purification. Longer use of blood purification or ventilation and a longer ICU stay were associated with functional deterioration. Intensivists should be aware of the effects of critical care procedures on functional deterioration and advance the appropriate use of functional support according to each patient's condition.