Research suggests that authenticity plays a positive role in one's career decision-making process but little is known of how this role unfolds over time. In the present study, we argue that authenticity positively relates to career decision self-efficacy over time, and vice versa. We conducted a study characterized by a three-wave longitudinal design with 459 Chinese university students over 1 year and examined the reciprocal dynamic effects of authenticity and career decision self-efficacy. Using a cross-lagged approach, we found that authenticity positively relates to career decision self-efficacy over time, and conversely, career decision self-efficacy also positively relates to authenticity over time. Our findings contribute to the literature on authenticity and career decision self-efficacy by demonstrating that they reciprocally promote each other. Our findings also have implications for university students, as well as educators and counselors who assist in facilitating the career decision process.