This research utilizes a unique, validated, multiple-choice exam design that allows researchers to observe and measure the degree to which students copy answers from their peers. Using data collected from the exam, this study investigates whether asking students to sign an honor code at the start of the exam reduced instances of cheating relative to a control group. Empirical results demonstrate that the classroom of students who signed the honor code had less overall copying of answers and also fewer individual students who engaged in cheating. This study contributes to the literature by conducting analysis on a sample that measures actual cheating frequency, as opposed to relying on reported cheating in surveys, and by demonstrating that a positive intervention can effectively discourage unethical behavior.