The past decade has witnessed the advent of task-based instructional approaches in different names including problem-based learning, situated learning and case-based learning. Though varied in names, they all seem to have one thing in common; they get learners involved with tasks or problems as contrasted with more traditional topic-centered curriculum approaches. (Merrill, 2007). Proponents of task-based learning believe that learners involved with real-world problems form appropriate schema and mental models as they collaboratively solve problems and reflect on their experience. Task-based instructional approaches have been widely adopted across a wide variety of discipline areas including medical training, social work, design, and language learning. This paper will discuss the implication of the task-based approach to second language learning where the method has been increasingly adopted and tried in many language classrooms across the world in the recent past. In this paper, the impact of task-based language learning will be explored with special regard to adult learners whose distinctive characteristics make task-based approaches more plausible and beneficial.Task-based instruction is a small, yet fast growing, trend in contemporary second language teaching. To give an example, the ERIC database shows over 120 articles on this issue since the beginning of this millennium. In order to discuss task-based learning properly, it is important to understand what the term 'task' means. Task has been defined by various researchers including Nunan (2004) who wrote that "a task is a piece of classroom work that involves learners in comprehending, manipulating, producing or interacting in the target language" (p.9). Earlier than Nunan, Jane Willis (1996) defined task as "an activity where the target language is used by the learner for a communicative purpose (goal) in order to achieve an outcome" (p.23). While definitions vary somewhat among scholars, they all emphasize that pedagogical task involves "communicative language use where users' attention is focused on meaning rather than grammatical form"