For the thousands of health systems recognized as Age-Friendly, considerable progress has been made to integrate 4Ms into clinical care. This study evaluated associations between 4Ms documentation and patient characteristics in an inpatient setting. In this prospective cohort, hospitalizations included were from patients in an Acute Care for Elders (ACE) unit where the 4Ms were adopted and implemented. Each M (What Matters, Medication, Mentation, and Mobility) was stratified into three categories (not documented, partly documented, and fully documented) reflecting "assessment" and "action" clinical care processes. Electronic health records were reviewed for patient and hospitalization characteristics. Descriptive statistics evaluated these characteristics across categories of each M. There were 620 hospital encounters (573 patients) included in the cohort. Patients had a median age of 80 years [IQR 76, 86] and 85% were White. Of all 4Ms, What Matters had the lowest documentation with 413 (67%) of encounters falling into the not documented group. Medication had the highest documentation with 453 (73%) of encounters in the fully documented group. Significant differences in documentation were associated with age and partlyversus fully documented Mobility (80 [76, 86] and 82 [77, 88] (p = 0.019)). Hospital length of stay was differentially associated with documentation of all 4M categories. Initial mobility scores were associated with not versus partly documented Medication (6 [2, 7] and 2 [2, 6] (p = 0.041)). We developed a structured way to categorize "assessment" and "action" 4Ms care processes reflective of three documentation categories in the hospital (not, partly, and fully) and identified important patient and hospital characteristics associated with each. These results offer opportunities for future improvement efforts and insight to which characteristics may be important to measure with wider 4Ms adoption and uptake.