Extended reality (XR) technologies such as virtual reality, augmented reality, and mixed reality are increasingly used in healthcare settings, complementing the digital transformation of healthcare. Effective adoption and use of XR necessitates high-quality evidence on factors associated with XR implementation in different healthcare contexts. This systematic umbrella review aimed to provide a state-of-the-art synthesis of critical factors of XR implementation in healthcare from systematic reviews and meta-analyses. A total of 2494 citations were identified from multiple databases and were evaluated using pre-determined eligibility criteria. Finally, 25 reviews representing 947 studies were synthesized using a socio-ecological framework. The findings suggest that XR implementation is associated with individual factors (e.g., immersive experience, technostress, training), interpersonal factors (e.g., user engagement, caregiver support, supervision), and institutional or systems-level factors (e.g., XR systems resources, technology adoption practices, accountability). This synthesis may inform future development of XR applications in healthcare, addressing critical factors using evidence-based approaches.