In this chapter, we draw on the conceptualization of mathematical curiosity by Peterson and Cohen (Educ Psychol Rev 31:807–832, 2019) to not only show how problem posing can be used to assess students’ mathematical curiosity but also how mathematical curiosity can be nurtured through problem posing. We argue that problem posing inherently involves curious aspects. We explicitly distinguish mathematical curiosity exhibited in problem posing and mathematical curiosity nurtured through problem posing. In particular, this chapter provides various examples of how mathematical curiosity is exhibited in students’ problem posing. Problem posing is a promising avenue through which to develop mathematical curiosity given that problem-posing tasks are typically very engaging, and students are motivated to discover new things to fill in gaps in their knowledge. We end this chapter by describing the challenges we face to systematically assess students’ mathematical curiosity and develop problem-posing interventions to nurture mathematical curiosity.