<p>Self-Determination Theory’s (SDT) perspective on values (intrinsic vs. extrinsic in nature) is useful to help understand and promote psychological well-being, but little is known about how to induce change in these values. Interestingly, though values are at the core of efficacious Acceptance and Commitment Therapy (ACT) interventions, the content of participants’ values has not been examined. Integrating basic value research anchored in SDT, we assessed the impact of an ACT intervention, Korsa, on university students’ intrinsic and extrinsic values. We also examined whether the importance they ascribed to these values after the intervention could mediate Korsa’s impact on life fulfillment. Participants (<i>N</i> = 137) were randomly assigned to this 5-session intervention or a waitlist and completed pre-and post-test questionnaires. The results of this randomized controlled trial (RCT) revealed that Korsa led to decreases in extrinsic values’ importance, as well as to increases in life fulfillment. However, there was no significant impact on intrinsic values, possibly due to a ceiling effect. Further, path analyses offered limited evidence that post-intervention values mediated Korsa’s impact on life fulfillment. In addition to advancing knowledge about how extrinsic values can be changed and well-being improved, this RCT sheds light on new potential mechanisms of action at play in ACT. Replication seems warranted, particularly with more heterogeneous samples.</p>