Essentially a sociological concept developed by several classical and contemporary theorists, alienation is a condition in social relationships reflected by a low degree of integration or common values and a high degree of distance or isolation between individuals or between an individual and a group in a community or work environment. Alienation is closely aligned with the concept of mastery, which is typically defined as a state of mind in which an individual feels autonomous and experiences confidence in his/her ability, skill, and knowledge to control or influence external events. The greater the level of alienation an individual experiences in a community or work setting, the weaker will be his/her sense of mastery. For police officers, a strong sense of mastery is particularly vital in relation to proactive law enforcement. This study of the impact of police alienation from the community on police decision-making and proactive policing involved a survey of police officers from 11 law enforcement agencies in the midwestern United States. The officers were grouped into three categories (high-, moderate-, and low-urban) based on the degree of urbanism of the community they served. A survey questionnaire was developed to measure respondents' level of perceived alienation, sense of mastery, and willingness to respond proactively both before and after three well-publicized "anti-police" court verdicts. Statistical analysis revealed a significant negative relationship between officers' alienation and mastery scores. These results support the predicted relationship between these factors. These findings suggest the need for creative approaches to reducing the impact of alienation on police performance. Some approaches are suggested in this article.