This study investigates /l/‐darkening in the Welsh and English speech of bilinguals in North Wales. Although it is claimed that /l/ is dark in all syllable positions in northern varieties of both languages, there have been no quantitative investigations of this feature which consider cross‐linguistic phonetic differences, the differing nature of language contact between North East and North West Wales, and differences in the way both languages are acquired by speakers. The dataset of 32 Welsh‐English bilinguals, aged 16–18, was stratified by speaker sex, home language, and area. Tokens of /l/ in word‐initial onset and word‐final coda positions were analysed acoustically. The results show cross‐linguistic differences in onset position and that such differences were found to be greater in the speech of female speakers. Differences were also found between the two areas. These results are discussed with reference to the influence of extra‐linguistic factors on speech production and the possible social meaning associated with dark /l/.