Given the growing public concern and attention placed on cases of research misconduct, government agencies and research institutions have increased their efforts to develop and improve ethics education programs for scientists. The present study sought to assess the impact of these increased efforts by sampling empirical studies published since the year 2000. Studies published prior to 2000 examined in other meta-analytic work were also included to provide a baseline for assessing gains in ethics training effectiveness over time. In total, this quantitative review consisted of 66 empirical studies, 106 ethics courses, 150 effect sizes, and 10,069 training participants. Overall, the findings indicated that ethics instruction resulted in sizable benefits to participants and has improved considerably within the last decade. A number of specific findings also emerged regarding moderators of instructional effectiveness. Recommendations are discussed for improving the development, delivery, and evaluation of ethics instruction in the sciences.