A theoretical model called 'Curriculum Design Coherence' (CDC) is described and justified. The model's purpose is to assist teachers in the compulsory and higher education sectors to design courses that can accommodate the complex and interdependent relationship between concepts and content and between knowledge and skills. Its intended usefulness as a curriculum design tool may also contribute to teachers' pedagogical decision-making. The model was initially developed in a New Zealand university Engineering study and is now being trialled in a study in the compulsory schooling sector with the 'Knowledge-Rich School Project'. The CDC model integrates concepts, content and competencies in a coherent way, thereby avoiding several tendencies which have affected curriculum studies in recent decades. These are: a 'skills' versus 'concepts' bifurcation; an over-emphasis on fragmented content without conceptual integration; and a similar over-emphasis on pedagogy (the 'how') at the expense of what is taught. The first sections of the article discuss the theories used to justify the model's connections between the elements of concepts, content and competencies. The theories concern (1) knowledge types (disciplinary and socio-cultural) and (2) knowledge forms (propositional/conceptual and procedural/competencies). The justification is followed by a description of the CDC model itself.