Objectives To determine functional status and mortality rates after colon cancer surgery in older nursing home residents. Design Retrospective cohort study. Setting Nursing homes in the United States. Participants Six thousand eight hundred twenty-two nursing home residents aged 65 and older who underwent surgery for colon cancer in the United States between 1999 and 2005. Measurements Changes in functional status were assessed before and after surgery using the Minimum Data Set Activity of Daily Living (MDS-ADL) summary scale, a 28-point scale in which score increases as functional dependence increases. Regression techniques were used to identify patient characteristics associated with mortality and functional decline 1 year after surgery. Results On average, residents who underwent colectomy had a 3.9-point worsening in MDS-ADL score at 1 year. One year after surgery, rates of mortality and sustained functional decline were 53% and 24%, respectively. In multivariate analysis, older age (≥80 vs 65-69, adjusted relative risk (ARR) = 1.53, 95% confidence interval (CI) = 1.15-2.04, P <.001), readmission after surgical hospitalization (ARR = 1.15, 95% CI = 1.03-1.29, P =.02), surgical complications (ARR = 1.11, 95% CI = 1.02-1.21, P =.01), and functional decline before surgery (ARR = 1.21, 95% CI = 1.11-1.32, P <.001) were associated with functional decline at 1 year. Conclusion Mortality and sustained functional decline are common after colon cancer surgery in nursing home residents. Initiatives aimed at improving surgical outcomes are needed in this vulnerable population. © 2012, Copyright the Authors Journal compilation © 2012, The American Geriatrics Society.