In the following chapter, I aim at describing the reasons to inquire about English language in-service (ELI hereafter) teachers’ ecologies of knowledges. The quest for ELI teachers’ knowledges is informed by theoretical tenets of the Epistemologies of the South (De Sousa Santos, 2007, 2009, 2010) poststructuralism in English language teaching (ELT henceforth) (Baxter, 2003), and postcolonial thought (Díaz, 2003). It is my intention to show that as ELI teachers’ knowledges have not been considered when framing public policy in ELT (Cárdenas, 2004, González, 2007) or -in my view- as an asset in the field, such knowledges might not have been sufficiently explored leading to a waste of valuable experience. I have brought up the concept of ‘ecologies of knowledges’, on the one hand because this concept entails the co-existence of different ways of knowing within ELI teachers’ construction of their being as professionals in the ELT area –co-existence that is still underexplored. On the other hand, I intend to understand how ELI teachers interrelate to such knowledges. I explore a philosophical understanding of knowledge starting with Plato and then I introduce a Foucauldian perspective. I also provide a glance towards a problematization of knowledge within ELT while finding some existing tensions in this field in regards to ELI teachers’ knowledge which I back up with empirical data. I attempt to show that ELI teachers have not been recognized as intellectuals (Giroux, 1997) and such an experience is being wasted, epistemologically speaking. An ecology of knowledges sheds light towards how institutional, personal and other types of knowledge co- exist with one another in the conformation of ELI teachers’ beings.