This study examines International Baccalaureate (IB) Diploma Programme (DP) students’ post-secondary educational aspirations, using a large international dataset of DP students (2016–2018). A total of 699 students responded to surveys at the beginning of the programme and upon completion of their DP examinations. The study found that DP students had very high academic aspirations both at the start and end of the programme. By the end of the DP, 98% of students aspired to at least a bachelor’s degree and 81% aspired to a master’s, doctoral or professional degree; additionally, 61% of DP students aspired to a very good or top-level university. Aspirations shifted slightly at the individual level for some students as they got closer to high school graduation, yet overall levels remained very high. A closer inspection of which factors contributed to differences in aspirations at the start of the DP revealed that certain personal characteristics of students, such as parental education and prior academic achievement, accounted for much of the variance. Interestingly, the proportion of DP teachers in a school was positively associated with aspiring to a very good or top-level university, which suggests that offering more school-level opportunities to participate in the DP encourages higher student aspirations.