According to the Swedish curriculum, entrepreneurship is to permeate all teaching in primary school. However, little is known about how entrepreneurship influences the teaching of different subjects. This paper reports on an educational design research study investigating the potential in combining entrepreneurship and mathematics in primary school. Two examples are given of how mathematics teaching changes when entrepreneurship enters mathematics lessons. The results indicate that there may be a win-win situation between mathematical and entrepreneurial competences, at least when it comes to creativity and tolerance for ambiguity.