<p>This article studies the role of defining cores – used products entering remanufacturing processes – in product development for systematic remanufacturing activities. Three companies in the heavy-duty and off-road vehicles industry with different levels of remanufacturing maturity were analysed through an explorative multiple case study to find out how core definition in product development affects remanufacturing activities. The results show that core definition is a positive indicator of systematic remanufacturing processes regardless of the size of the remanufacturing portfolio or the maturity of remanufacturing activities. Based on the findings, a three-phase model of core definition is suggested for the early phases of product development. The findings of this study show that design for remanufacturing should include systematic definition of cores, and communication between remanufacturing activities and product development is crucial for its success. Thus, this study shows the importance of aligning product development activities with the needs of remanufacturing and defining cores in the early stages of product development.</p>