Many U.S. military veterans experience difficulties reintegrating into civilian society after their military service, especially veterans with chronic mental illness. Few studies have examined the sense of citizenship among veterans and citizenship has rarely been examined in psychological studies. As part of a larger experimental trial, this study piloted the Yale Citizenship Scale on a sample of 199 U.S. veterans with chronic mental illness in Connecticut and Houston. A factor analysis found that the scale comprised 7 factors labeled as Personal Responsibilities, Government and Infrastructure, Caring by Others, Civil Rights, Legal Rights, Choices, and World Stewardship. Veterans with chronic mental illness reported moderate scores on each factor and the total scale. Each factor as well as the total scale showed good convergent validity with mental health and quality of life measures and discriminant validity from pain and physical health measures. The total scale and its factors demonstrated acceptable‐to‐excellent internal consistency and there was fair‐to‐excellent test‐retest reliability on 6 of the 7 factors. Together, the findings demonstrated that the Yale Citizenship Scale can be adapted for use for U.S. veterans with chronic mental illness and that helping veterans achieve high levels of citizenship may an important social and clinical goal.