The aim of the study is to explore English language teachers' implementation of a curriculum innovation with an action-oriented approach in the context of teaching English to very young learners in Turkish primary schools. As a part of exploratory case study design, data from multiple sources were gathered in the form of observational field notes, followup interviews and document analysis. Findings indicated a variation in teachers' instructional practices ranging from traditional to constructivist. Even if factors such as presence of instructional materials and facilities of the school influenced the implementation, this study indicated that the teacher is the main factor in effective delivery of any imposed change. Besides, the positive influence of proficiency in subject-matter knowledge and curricular knowledge to achieve coherence between the intended and delivered curriculum was revealed. The results showed that providing an ongoing support and including teachers in the process of curriculum development helped to promote the effective implementation of the curriculum innovation.