Introduction Communication is a fundamental human right and should not be constrained by disability; advances in modern technology are reshaping how communication is conceived and delivered, creating new possibilities for people who rely on augmentative and alternative communication (AAC). This systematic review examined whether immersive virtual, augmented, and mixed reality (VR/AR/MR; hereafter referred to as XR) has been integrated with brain-computer interfaces (BCIs) to support AAC for people who rely on it, and what evidence exists regarding usefulness and usability. Methods Searches were conducted in five databases, with the initial search completed on 30 June 2021 and the updated search completed on 18 November 2025. Results Two eligible studies were included. The evidence base was limited and methodologically heterogeneous, spanning distinct integration pathways: (i) an immersive-display implementation of a classic P300 speller suggesting communication performance comparable to conventional displays; and (ii) a wearable mixed-reality AAC concept contrasting non-BCI access (eye-gaze) with BCI-based access, with non-BCI access appearing more practically usable while BCI access remained challenging. Overall, the included studies indicate that immersive XR platforms can technically accommodate BCI-mediated interaction for communication-related purposes. Discussion Current evidence remains sparse and heterogeneous, with usability and usefulness varying by application target and evaluation endpoint. This review therefore synthesises the available feasibility and usability/usefulness evidence and offers an open discussion of design and evaluation priorities for advancing BCI-enabled immersive AAC toward practical use in people who rely on it. Systematic review registration https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021273338 , identifier: CRD42021273338.