Objective: Uptake of advance care planning (ACP) in cancer remains low. An emphasis on personal value discussions and adoption of novel interventions may serve as the catalyst to increase engagement. This study examined the effectiveness of a video decision support tool (VDST) modelling values conversations in cancer ACP. Methods: This single site, open-label, randomised controlled trial allocated patient-caregiver dyads on a 1:1 ratio to VDST or usual care (UC). Previously used written vignettes were converted to video vignettes using standard methodology. We evaluated ACP document completion rates, understanding and perspectives on ACP, congruence in communication and preparation for decision-making. Results: Participants numbered 113 (60.4% response rate). The VDST did not improve overall ACP document completion (37.7% VDST; 36.7% UC). However, the VDST improved ACP document completion in older patients (≥70) compared with younger counterparts (<70) (OR=0.308, 95% CI 0.096 to 0.982, p=0.047), elicited greater distress in patients (p=0.015) and improved patients and caregivers ratings for opportunities to discuss ACP with health professionals. ACP improved concordance in communication (VDST p=0.006; UC p=0.045), more so with the VDST (effect size: VDST 0.7; UC 0.54). Concordance in communication also improved in both arms with age. Conclusion: The VDST failed to improve ACP document completion rates but highlighted that exploring core patient values may improve concordance in patient-caregiver communication. Striving towards a more rigorous design of the VDST intervention, incorporating clinical outcome scenarios with values conversations may be the catalyst needed to progress ACP towards a more fulfilling process for those who partake in it. Trial registration number: ACTRN12620001035910.