Purpose: The purpose of this paper is to examine threshold concepts in the context of teaching and learning first-year university economics. It outlines some of the arguments for using threshold concepts and provides examples using opportunity cost as an exemplar in economics. Design/ Methodology/Approach: The paper provides an overview of the theoretical literature around threshold concepts in economics and provides exemplars from previous research, and current practice, to illustrate how they might be applied in economics. Findings: The notion of threshold concepts such as opportunity cost can be extremely useful in pedagogic design. They focus on how learning concepts changes student thinking, rather than the standard approach which treats many concepts as equal in importance. Designing appropriate instructional materials around threshold concepts is time consuming and this may prove a barrier to the notions widespread adoption. Originality/Value: This paper contributes to the literature discussing the practical application of threshold concepts in teaching first-year economics as well as identifying possible reasons for its relatively slow adoption as a teaching tool in university.