English language learners (ELL) have dedicated considerable time and effort to the development of their language proficiency. This has included the use of a variety of mobile assisted language learning (MALL) tools that are either unproven or that have undergone limited evaluations of their effectiveness. I propose and demonstrate the feasibility of an adaptive MALL approach that aims to scaffold ELL vocabulary and communication needs. This scaffolding recommends learning materials to ELLs by employing the ecological approach to dynamically reason over logs of learner interactions with a MALL tool. The personalized approach to supporting learners that is provided by this tool was developed following user-centered design principles before the tool was evaluated through two studies. These studies investigated its influence on ELL vocabulary knowledge, communication, and affect. The first study focused on the relationship between student vocabulary knowledge and system usage. The second study aimed to determine the relationships among system usage, user communicative success, and user affect. These summative evaluations and the formative evaluations that were used to build the MALL tool show that the proposed approach can support ELL communication, vocabulary development, and affect. Going forward, similar approaches will be used within a MALL tool that aims to support the development of the reading comprehension of low-literacy adults.