Mathematics is often perceived as a stand-alone subject in the school curriculum. When used as a tool to examine cross-curricular content, mathematics can enable deeper understanding of the context under investigation (Makar & Confrey, 2007). A study was designed to investigate opportunities and challenges that emerged when students addressed authentic interdisciplinary problems using an inquiry-based approach. This paper aims to identify aspects of students' engagement across two cohorts of a year 5 (age 9-10) classroom in Australia. Using a framework developed by Kong, Wong & Lam (2003), the paper discusses students' affective, behavioural, and cognitive engagement with mathematics during four integrated curriculum units over the course of a year. Results suggest that in both cohorts, students initially struggled with the shift from teacher-directed to student-driven learning within an inquiry-based, interdisciplinary environment. By the end of each year, however, the students had developed observable improvement in their ability to engage on multiple dimensions within the framework with ill-structured mathematical problems encountered across content areas. Implications for mathematics education research are addressed.