Action research is geared to changes for the better and has the potential to assist teachers to extend their teaching skills and develop a deeper understanding of themselves, their classroom and their learners. However, in the area of applied linguistics, the viability of action research has been seriously questioned. In this article, we argue that adopting a complexity-theory perspective, which requires teachers to be dynamic and complex in their approach, helps in identifying action research as a suitable research tradition for investigating second-language classrooms and in turn using it widely to invigorate the field of applied linguistics. Our argumentation is supported by the fundamental links between action research and complexity theory as an emerging paradigm in education. Although the case made in this article concerns second-language classrooms, the conclusions reached may well apply to any classroom that shares some commonalities with second-language classrooms. (Contains 1 note, 1 table, and 1 figure.)