Abstract Mobile-assisted language learning, involving the use of various portable electronic devices, is an increasingly popular way to study a second language (L2). However, claims made about the potential for L2 learning through app use by commercial companies need further investigation. This chapter examines mobile-assisted language learning considering ISLA theories and empirical research, focusing on the potential for in-class and extracurricular L2 learning. In addition, the role of motivation for L2 app use is given special consideration, especially because of the large attrition rates found in multiple app studies. The chapter also identifies ways in which app-based research can expand its scope by focusing on issues of diversity, equity, inclusion, and justice. In particular, research on (a) languages other than English, (b) younger and older learners, (c) higher proficiency learners, and (d) learners in lower resource contexts is needed. Pedagogically, the chapter focuses on the use of apps both inside the classroom and as an extracurricular activity, emphasizing the need for teacher familiarity with apps and strategies for maintaining student motivation.