This conceptual paper aims to characterize science teachers' practical knowledge utilizing a virtue-based theory of knowledge and the Aristotelian notion of phronesis/practical wisdom. The article argues that a greater understanding of the concept of phronesis and its relevance to science education would enrich our understandings of teacher knowledge, its development, and consequently models of teacher education. Views of teacher knowledge presented in this paper are informed by philosophical literature that questions normative views of knowledge and argues for a virtue-based epistemology rather than a belief-based one. The paper first outlines general features of phronesis/practical wisdom. Later, a virtue-based view of knowledge is described. A virtue-based view binds knowledge with moral concepts and suggests that knowledge development is motivated by intellectual virtues such as intellectual sobriety, perseverance, fairness, and humility. A virtue-based theory of knowledge gives prominence to the virtue of phronesis/practical wisdom, whose primary function is to mediate among virtues and theoretical knowledge into a line of action that serves human goods. The role of phronesis and its relevance to teaching science are explained accordingly. I also discuss differences among various characterizations of practical knowledge in science education and a virtue-based characterization. Finally, implications and further questions for teacher education are presented.