Education for sustainable development (ESD) guides and empowers educators to reshape their thinking style and move towards a sustainable future. It has attracted a lot of attention and been studied in different perspectives. However, contextual factors have not been studied in relation to sustainable development for teacher education. Therefore, this study aims to find out the possible effects of changing contextual factors on pre-service and in-service teachers in terms of sustainable education for their profession. For this purpose, 267 pre-service teachers from four different universities and 50 in-service teachers from 15 different cities participated in the study. Out of 317 participants, 245 stated that contextual factors influence their teaching habits adversely, while 54 reported that they ignored the outer factors. In light of the data gathered, it can be said that the participant teachers were mostly pessimistic about the effect of contextual differences on ESD. Based upon participant statements, a new theory emerged. According to this theory, there are personal (P), institutional (I), stakeholder-related (S), environmental (E) and training-related (T) factors which positively and/or negatively influence ESD in teacher education. In this regard, the new theory was formed with the first letters of the related factors and called P.I.S.E.T. These findings suggest that pre-service teachers should be exposed to various school settings during their practicum and in-service teachers should receive context-related support from the stakeholders to enhance their professional skills and act in line with the principles of ESD.