This thesis studies the usability issues of the mobile phone in informal Swedish language learning. The concept of usability is defined by expanding the technical usability attributes of Jakob Nielsen with other recent attributes derived from considering the technical aspects of mobile learning (m-learning). Thus, the ultimate structure of the usability factors that are discussed in this study consists of: accessibility, easy-to-learn, technical design, efficiency and satisfaction. With the support of the relevant previous literature and interview, we research this topic by considering the mobile-assisted language learning (MALL), informal language-learning and usability elements, in order to explore and identify the usability of mobile phone. The goal of this study is to contribute to detailed understanding of mobile phone usage, further identify the usability issues of mobile phones by obtaining both critical and commendatory feedbacks and reflections from the users. For final results, through qualitative research approach, we offered several findings regarding the mobile phone usability with specified reasons.