Previous studies have indicated that computers and the internet play very important roles in students' acceptance and use of new information technology. In recent years, with the rapid development of mobile technology, mobile learning (m-learning) has becoming another popular topic. However, little is known about the students' attitudes and self-efficacy with the use of a mobile device in language learning. The purpose of this study was to investigate the attitudes and self-efficacy of using mobile learning devices for college students in a language class by employing task-based instruction. The sample group of the study comprised 58 second-year students at a technical university in central Taiwan who used mobile devices for m-learning in an English class to complete assigned tasks under the guidance of the instructor. Results showed that most students agreed that their motivation for English learning was enhanced and most of them had positive attitudes towards m-learning. Implications for future research and the practice of m-learning are discussed. (Contains 6 tables.)