Investigating the “knowing”, a module of the KARDS model proposed by Kumaravadivelu (2012) for teacher education, of Iranian teachers of learner autonomy, this study is an attempt to illuminate some of the yet unexplored areas of teachers’ various types of knowledge of learner autonomy. Furthermore, it attempts to illustrate how Iranian Non-EFL teachers’ knowing affects their practices with regard to learner autonomy and how this could differ from that of Iranian EFL teachers. To that end 112 EFL and Non-EFL teachers were purposefully cluster-sampled. Based on convenient sampling but only after data saturation was reached were 12 teachers interviewed. Based on the result of the interviews and the data gleaned from the literature a questionnaire was developed. The sample were asked to complete the questionnaire and then through negative case analysis some were interviewed. The questionnaire tapped into the social, political, psychological and personal aspects of learner autonomy. The results indicated the informants, be it EFL or non-EFL, found learner autonomy to be a psychological construct, which can be traced back to their personal knowledge. Finally, with regard to the feasibility and desirability of learner autonomy implementation in the education system, the informants see learner autonomy as more of a desirable concept than feasible. It is hoped that teachers and teacher educators find the results as well as the suggestions-for-action made at the end of the study helpful and that the results have tangible implications for the Iranian education system when fed into professional development activities and strategic planning.