Background <p>Awake surgery with intraoperative language mapping has become increasingly refined, allowing assessment not only of motor but also higher brain functions. Language remains the most critical function to evaluate and preserve. However, reports of multilingual patients undergoing such procedures are still limited, particularly those involving Japanese, a linguistically and structurally unique language.</p> Case description <p>We present the case of a 32-year-old right-handed multilingual male (Japanese L1, English L2, French L3), a film director and actor, who underwent awake craniotomy for a recurrent low-grade glioma involving the left temporal lobe. Preoperative functional MRI confirmed left hemispheric language dominance across all three languages, although French and English showed broader activation than Japanese during semantic fluency tasks. During surgery, cortical mapping with object naming and reading tasks was performed in Japanese, English, and French. Naming errors were observed in the posterior superior temporal gyrus across all three languages, whereas semantic paraphasia in the posterior middle temporal gyrus and reading impairment in the posterior inferior temporal gyrus were specific to Japanese. Postoperative MRI revealed subtotal resection with preservation of language function. Histopathology confirmed astrocytoma, IDH-mutant, WHO grade 3.</p> Conclusion <p>This case represents the first report of intraoperative language mapping in a Japanese–English–French trilingual patient, demonstrating both overlapping and language-specific cortical regions. The findings underscore the importance of individualized and multimodal language mapping in multilingual patients, particularly when typologically distant languages such as Japanese are involved.</p>