Virtual Reality (VR) serious games offer significant potential for augmenting existing methods in medical education and therapy. Despite their advantages, widespread adoption in healthcare remains limited due to the substantial expertise, time, and financial investment required for development. In this paper, we introduce VIA-VR, a novel platform that empowers healthcare professionals to create immersive VR serious games by enabling collaborative workflows where software engineers develop reusable building blocks that healthcare experts can assemble into tailored VR experiences. Our work presents both the platform’s concept, including the idea, workflow, and architecture, and the initial implementation that can be built upon. In particular, VIA-VR targets applications where a trainee or patient is immersed in a virtual environment (VE) using a consumer-grade head-mounted display (HMD), and a supervisor monitors the session—often the same individual who has authored or adapted the VR experience. To minimize development efforts and ensure long-term extensibility of the provided functionalities, we combine established software solutions with new domain-specific modules. VIA-VR’s features include a VE editor, a story editor, a polygon reduction tool for geometry optimization, a behavior editor based on building blocks (eliminating the need for scripting), a photogrammetry-driven virtual character creation tool, and a physiological data measurement engine. We present two minimal demos that have been created with the first iteration of the platform: a VR exposure therapy application for pyrophobia and a gait rehabilitation exercise application. As an open-source platform, VIA-VR strives to contribute to open standards for developing medical VR serious games, aiming to accelerate innovation and improve accessibility in healthcare.