jats:titleAbstract</jats:title> jats:pSocial interactions that take place during study abroad in linguistically rich settings are important for oral proficiency development; however, few studies have explicitly examined the underlying network structure of students’ social experiences in study abroad contexts and its role in oral proficiency development. This mixed-methods research examined the relationship between self-reported social network structures and self-perceived English oral proficiency gains among 88 Chinese international students at a UK university. While the majority of participants’ networks consisted of Chinese-speaking peers, most of them managed to develop strong and frequent relations with English-speaking peers. Students reported gains in oral proficiency, especially in areas related to language use that require higher levels of proficiency. Diverse networks with significant and high-frequency English-speaking relationships were more likely to be associated with L2 oral proficiency gains, while dense networks with only frequent and strong in-group relationships could potentially limit L2 development.</jats:p>