The present study sought to explore how English language learners (ELLs) used Instagram, a popular social networking site, for language learning purposes and to reveal their attitudes towards and experiences in using it as a mobile-assisted language learning (MALL) tool. Special interest was also placed on whether there were any distinct ELL profiles in using Instagram for independent and informal language learning. In this mixed-methods study, both quantitative and qualitative data were concurrently collected through an online comprehensive survey consisting of three sections. Ninety-seven Instagram using ELLs took part in this study. Basic descriptive statistics and a cluster analysis were conducted on the quantitative data, and a thematic analysis on the qualitative data. The results showed that Instagram has the potential to help ELLs to improve overall language skills in general, and vocabulary and communication skills in particular. Further, ELLs' experiences in using Instagram as a MALL tool for informal language learning were largely positive. Additionally, two different language learner profiles (i.e., novice and experienced) emerged based on Instagram use habits and orientations. Overall, this study indicated that social networking platforms and MALL applications can be used as an effective mobile language learning tool.