Traditional cultural heritage, often damaged or limited to static displays, struggles to fully convey its profound significance. The rapid advancement of the Internet of Things (IoT) and Extended Reality (XR) technologies has introduced transformative solutions to the preservation, restoration, and interactive display of cultural heritage. IoT enables real-time data acquisition, multi-device connectivity, and dynamic interactions, while XR enhances cultural heritage engagement through immersive experiences and precise digital reconstructions. This paper provides a comprehensive review of the synergistic application of IoT and XR in cultural heritage, focusing on three key areas: 3D reconstruction and restoration, smart guidance, and immersive experiences. In 3D reconstruction and restoration, this review explores how IoT’s efficient data acquisition and transmission capabilities integrate with XR’s high-precision visualization techniques to improve accuracy and efficiency in heritage preservation. For Intelligent Guided Tour, this review analyzes how IoT-enabled device collaboration and real-time updates enhance XR-based personalized and interactive tour experiences. In immersive experiences, this review examines how IoT’s multi-source data sensing combined with XR’s multisensory interaction creates more engaging and participatory environments for users. The review also synthesizes existing user evaluation methodologies and identifies key challenges in the convergence of IoT and XR, including device compatibility, data transmission latency, cost, and privacy concerns. Future directions are proposed, such as advancing multimodal data processing, establishing open technical standards, and developing cost-effective solutions for broader adoption. This study highlights the immense potential of IoT and XR to revolutionize the preservation, understanding, and experience of cultural heritage, providing valuable insights for future research and applications.