Research in second language teacher education has demonstrated that novice teachers have difficulty in using their pedagogical knowledge, which partly results from a heavy focus on theory offered in teacher training programs (e.g., Bartels, 2005, 2009; Tarone & Allwright, 2005). In order to better equip student teachers with the knowledge necessary to teach, courses should include learning situations through which second language teachers can move from practice to theory (e.g., Kumaradivelu 1999; Tsui, 2003). Such an approach would seem particularly important in practicum courses, because it is known that student teachers develop by studying their own practice (Mann, 2005). In the last decade, this approach has received great interest among researchers studying the impact of multilingualism on second language acquisition courses (e.g., Angelova, 2005; Thompson & Erdil, 2015). This article reports on the author's introspective case study involving the learning of a third language and its impact on her classroom practices. It describes how the learning of Czech, through diary writing, influenced her as a practicum teacher. As a result, she proposes a technique in which student teachers can be engaged in situated learning tasks using a third language, with the purpose of having them reflect on their own practices and increase their pedagogical knowledge.