The aim of this case study was to describe differences in English and British Sign Language (BSL) communication caused by a left temporal tumour resulting in discordant presentation of symptoms, intraoperative stimulation mapping during awake craniotomy and post-operative language abilities. We report the first case of a hearing child of deaf adults, who acquired BSL with English as a second language. The patient presented with English word finding difficulty, phonemic paraphasias, and reading and writing challenges, with BSL preserved. Intraoperatively, object naming and semantic fluency tasks were performed in English and BSL, revealing differential language maps for each modality. Post-operative assessment confirmed mild dysphasia for English with BSL preserved. These findings suggest that in hearing people who acquire a signed language as a first language, topographical organisation may differ to that of a second, spoken, language.