Objective: This study aimed to develop a 3-week gratitude intervention program that included gratitude lists and behavioral gratitude expression and to examine the effect of the program on work engagement, gratitude, self-efficacy, psychological distress, and job performance in a pretest-posttest study design. Methods: Eight hundred thirty-five employees were recruited for the study. The outcomes were measured at baseline, postintervention, and at 6-week follow-up. Estimated means at the three points were compared in a mixed model for repeated measures. Results: One hundred forty-five workers were included and analyzed. Work engagement showed no significant improvement after the intervention. However, gratitude, self-efficacy, psychological distress, and job performance improved significantly. Conclusions: The program might be effective for improving gratitude, self-efficacy, psychological distress, and job performance, but further modification of the program is needed to improve the effect on work engagement.