The new Australian Curriculum (AC) aims to prepare learners for the twenty-first century and in doing so, emphasize the development of critical (and creative thinking) as one of the "general capabilities" of learners. Critical thinking is seen as key in preparing "students to live and work in the 21st century" and "fundamental to effective learning". In light of the essential role critical thinking is accorded in the AC, this paper examines the understandings of critical thinking as found in it and in the literature with the aim to draw out the implications of these on AC teachers' practice and knowledge. The paper then identifies and examines the key challenges that may lie ahead in the realization of this key general capability. It also proposes ways in which these challenges could be mitigated to support teachers, who are the ultimate key agents of educational change, in their development of this general capability in their learners as emphasized in the new AC.