The design stage of a product plays a critical role in determining its sustainability. Key product attributes—such as reliability, durability, reusability, repairability, design for remanufacturing, recyclability, and end-of-life considerations—are established during this stage, influencing the product’s overall environmental impact. Circular product design (CPD) is a design philosophy that fosters economic growth while reducing negative environmental impact across the product’s entire life cycle. This study aims to identify circular product design strategies (CPDS) for the apparel industry, a sector known for its significant carbon footprint. Twelve CPDS are identified in this study, categorized into five dimensions of circular economy (CE): narrowing, slowing, closing, reintegrating, and technology, using the fuzzy Delphi method (FDM) with inputs from a panel of twenty-three experts. Furthermore, causal interrelationships and a prioritized list of these strategies are determined using the fuzzy decision-making trial and evaluation laboratory (DEMATEL) technique. Of the twelve strategies, five are part of the causal group, while the remainder are in the effect group. The top three causal CPDS are Design standardization, Design with responsible materials, and Design for redesign and remanufacturing. Conversely, the CPDS under the ‘effect’ group with least impact includes Multifunctional product design, Artificial intelligence in design forecasting, and Computer-aided product design. This study offers valuable managerial insights for decision-makers and designers in the apparel industry, guiding the implementing of CE practices throughout the apparel supply chain.