In order to teach about sustainability, teachers need to be able to translate their personal understanding of this concept into their pedagogy in ways that make it accessible to their learners. This translation process is known as pedagogical content knowledge (PCK). This study investigated the way that two teachers translated their understanding of sustainability into their pedagogy and the effects of this translation on children's learning (n?=?18). Two interpretive case studies were constructed. Data were generated using interviews and documents. Two frameworks were used to analyse the data. One was a definition of sustainability and the other a model of PCK expressed as pedagogical context knowledge (PCxK) that consisted of four components. The findings showed that the translation of sustainability was a complex interaction of three of the PCxK components with some use of the fourth. Some children developed an understanding of sustainability but only two were able to link their understanding with the scientific concepts taught resulting in "diffused learning". Also, these findings suggest that while the PCxK model used to analyse the translation process had a degree of precision and heuristic power, further refinement is needed in order for this model to explicate teachers' PCK.