Background <p>Virtual reality (VR)-based mindfulness intervention may be a potentially effective approach for stress relief in postgraduate students. This pilot study examined the preliminary effects of a VR-based mindfulness intervention on stress reduction among postgraduate students, in comparison with a conventional mindfulness intervention and a control condition. In addition, the study evaluated the feasibility, acceptability, and user experience associated with delivering mindfulness through VR technology.</p> Methods <p>A three-arm, assessor-blinded pilot randomised controlled trial was conducted. Forty-five full-time postgraduate students were randomly assigned (<i>n</i> = 15 per group) to a mindfulness group (15-minute audio-guided mindful practice twice a week for two weeks), a VR mindfulness group (VR-based mindfulness intervention twice weekly for two weeks), or a control group. The feasibility, acceptability, and preliminary effects of VR-based mindfulness intervention on relieving stress were examined. Individual semi-structured interviews were conducted with participants in the VR mindfulness group to explore their experiences following the intervention.</p> Results <p>This pilot study supported the feasibility of VR-based mindfulness intervention with satisfactory recruitment (54.88%), attrition (4.44%), and intervention completion (95.56%) rates. Participants in both the VR-based mindfulness group (<i>β</i> = -0.422, 95%CI: -0.804 to -0.039, <i>p</i> = 0.031, <i>g</i> = -0.42) and the mindfulness group (<i>β</i> = -0.563, 95%CI: -1.052 to -0.074, <i>p</i> = 0.024, <i>g</i> = -0.44) exhibited significant reductions in perceived stress scores compared to the control group at post-intervention. Additionally, significant reductions on total mood disturbance and negative mood were observed in both VR-based mindfulness group (<i>β</i> = -16.553, 95%CI: -28.800 to -4.306, <i>p</i> = 0.008, <i>g</i> = -0.52; <i>β</i> = -22.159, 95%CI: -40.827 to -3.491, <i>p</i> = 0.020, <i>g</i> = -0.52) and mindfulness groups (<i>β</i> = -16.004, 95%CI: -30.500 to -1.509, <i>p</i> = 0.030, <i>g</i> = -0.59; <i>β</i> = -23.029, 95%CI: -45.307 to -0.752, <i>p</i> = 0.043, <i>g</i> = -0.53). However, no statistically significant differences between groups were found in the total scores of mindfulness (<i>p</i> &gt; 0.05).</p> Conclusion <p>This pilot study demonstrated the feasibility and potentially preliminary effectiveness of VR-based mindfulness intervention for postgraduate students. Further multi-centre randomised controlled trials with a larger sample size and longer follow-up are recommended to ascertain the effects of VR-based mindfulness intervention for stress relief among postgraduate students.</p> Trial registration <p>This study has been registered in ClinicalTrials.gov (NCT05948280) on 17th July 2023.</p>