Background/Objectives: The increased availability of naloxone underscores the urgent need for scalable, effective training interventions. While current training modalities show promise, critical challenges persist, particularly regarding the development of interactive, self-efficacious platforms that mitigate anxiety in real-world overdose response, especially among laypersons. Therefore, this study aimed to develop and evaluate the usability and acceptability of a novel, self-paced mixed reality-based training tool (ReviveXR). Methods: ReviveXR was designed using the Apple Vision Pro spatial computing headset and Unity platform, employing mixed reality technology to facilitate interaction with virtual overdose scenarios while maintaining awareness of the physical environment. The intervention included a simulated tutorial and interactive modules on overdose response, rescue breathing, and chest compressions. Field testing was conducted in two rounds across various settings with a heterogeneous sample (N = 25), including individuals who use drugs, bystanders, first responders, and technology specialists. Data collection involved pre- and post-intervention surveys and qualitative interviews. Results: Participants demonstrated significant improvements in knowledge related to overdose recognition, naloxone administration, rescue breathing, and chest compressions. ReviveXR increased participants’ confidence and intent to help overdose victims while reducing uncertainty during overdose reversal. Participants were predominantly from rural areas and primarily identified as White and male. Qualitative feedback emphasized the platform’s heightened engagement, realism, patient responsiveness, and capacity to enhance knowledge acquisition and behavioral preparedness compared with conventional training approaches. Conclusions: ReviveXR offers a scalable, cost-effective, engaging alternative to traditional naloxone training programs, demonstrating strong feasibility across diverse environments and participants. ReviveXR holds considerable promise for expanding and enhancing community overdose response capacities and training healthcare professionals and first responders.