This report describes Diversion Alert, a unique online tool aimed at reducing misuse and diversion of prescription drugs, and reports the results of a 1-year evaluation of Diversion Alert's impact in Maine. We used a quasi-experimental research design to compare survey data in Maine with those of neighboring states (New Hampshire and Vermont, 2013 and 2014). Compared with their counterparts in New Hampshire and Vermont who did not use Diversion Alert, prescribers and pharmacists in Maine who used Diversion Alert increased their communication with patients and other providers involved in their patients' care, became aware of patients arrested for prescription drugs possession or diversion, used best practices associated with prevention or detection of addiction and diversion more frequently, and attributed positive changes in their prescribing practices to Diversion Alert. In combination with other state and federal programs, Diversion Alert may be an effective tool to help prevent the misuse of opioid medications.