The Internet of Things (IoT) has enabled manufacturing companies to create significant business opportunities by extending their product-based portfolios with innovative systems that integrate products, services, and customer data. While previous literature has addressed the technical characteristics and commercial benefits of these systems, more research is needed on what makes a successful IoT system design process that can be used as a guideline by designers within the context of manufacturing. This paper aims to address this gap using a comparative case study of two leading manufacturers from the aerospace and trucking industries. Based on empirical data, the commonalities and differences between the two companies are articulated. Further analysis of the cases revealed six antecedents for successful IoT service and system design: Communicating a well-articulated system design strategy, redefining frontline employee roles and responsibilities, training and recruiting service aware staff, providing guidance to customers on system use, aligning customer focus across the business, and utilizing methods/techniques for systems thinking and creativity. These antecedents are discussed in detail with evidence from two IoT system design projects. Consequently, the findings show that successful IoT implementations require more than solid product design; they also necessitate well-executed service and system design.