Objective To explore using the Patient Activation Measure (PAM) for identifying patients more likely to have ambulatory care–sensitive (ACS) utilization and future increases in chronic disease. Data Sources Secondary data are extracted from the electronic health record of a large accountable care organization. Study Design This is a retrospective cohort design. The key predictor variable, PAM score, is measured in 2011, and is used to predict outcomes in 2012–2014. Outcomes include ACS utilization and the likelihood of a new chronic disease. Data Our sample of 98,142 adult patients was drawn from primary care clinic users. To be included, patients had to have a PAM score in 2011 and at least one clinic visit in each of the three subsequent years. Principal Findings PAM level is a significant predictor of ACS utilization. Less activated patients had significantly higher odds of ACS utilization compared to those with high PAM scores. Similarly, patients with low PAM scores were more likely to have a new chronic disease diagnosis over each of the years of observation. Conclusions Assessing patient activation may help to identify patients who could benefit from greater support. Such an approach may help ACOs reach population health management goals.