Most students of English as a foreign language (EFL) lack sufficient opportunities to practice their English-speaking skills. However, the recent development of social-networking sites (SNSs) and mobile learning, and especially mobile-assisted language learning, represents new opportunities for these learners to practice speaking English in a meaningful way. This study integrated a mobile SNS into first-grade EFL classes in China, with the aim of determining its effects on the students' speaking skills. Two classes were recruited, one as a control group that did not use the SNS, and the other as the experimental group, which did. While both classes' speaking skills improved between pretest and posttest, the gains in English fluency by the experimental group were significantly larger. Progress in accuracy and pronunciation, on the other hand, were similar across the two groups. These findings are discussed in relation to specific characteristics of SNSs and mobile learning that enable learners to speak in low-stress, situated contexts.