Background: Cognitive frailty refers to a clinical syndrome in which physical frailty and mild cognitive impairment coexist.Motor-cognitive training and virtual reality (VR) have been used to launch various therapeutic modalities to promote health inolder people. The literature advocates that motor-cognitive training and VR are effective in promoting the cognitive and physicalfunction of older people. However, the effects on older people with cognitive frailty are unclear. Objective: This study examined the effects of VR motor-cognitive training (VRMCT) on global cognitive function, physicalfrailty, walking speed, visual short-term memory, inhibition of cognitive interference, and executive function in older peoplewith cognitive frailty. Methods: This study used a multicentered, assessor-blinded, 2-parallel-group randomized controlled trial design. Participantswere recruited face-to-face in 8 older adult community centers. Eligible participants were aged >= 60 years, were communitydwelling, lived with cognitive frailty, had no dementia, and were not mobility restricted. In the intervention group, participantsreceived VRMCT led by interventionists with 16 one-hour training sessions delivered twice per week for 8 weeks. In the controlgroup, participants received the usual care provided by the older adult community centers that the investigators did not interferewith. The primary outcome was global cognitive function. The secondary outcomes included physical frailty, walking speed,verbal short-term memory, inhibition of cognitive interference, and executive function. Data were collected at baseline (T0) andthe week after the intervention (T1). Generalized estimating equations were used to examine the group, time, and interaction(time x group) effects on the outcomes. Results: In total, 293 eligible participants enrolled in the study. The mean age of the participants was 74.5 (SD 6.8) years. Mostparticipants were female (229/293, 78.2%), had completed primary education (152/293, 52.1%), were married (167/293, 57.2%),lived with friends (127/293, 43.3%), and had no VR experience (232/293, 79.5%). In the intervention group, 81.6% (119/146)of participants attended >80% (13/16, 81%) of the total number of sessions. A negligible number of participants experienced VRsickness symptoms (1/146, 0.7% to 5/146, 3%). VRMCT was effective in promoting global cognitive function (interaction effect:P=.03), marginally promoting executive function (interaction effect: P=.07), and reducing frailty (interaction effect: P=.03). Theeffects were not statistically significant on other outcomes. Conclusions: VRMCT is effective in promoting cognitive functions and reducing physical frailty and is well tolerated andaccepted by older people with cognitive frailty, as evidenced by its high attendance rate and negligible VR sickness symptoms.Further studies should examine the efficacy of the intervention components (eg, VR vs non-VR or dual task vs single task) onhealth outcomes, the effect of using technology on intervention adherence, and the long-term effects of the intervention on olderpeople with cognitive frailty at the level of daily living.