This research puts forward a novel knowledge-supported design process for obtaining personalized ready-to-wear garment products aimed at consumers with atypical morphology by using a virtual a three-dimensional-to-two-dimensional (3D-to-2D) design method. The proposed design process starts with designing a personalized garment block, which is then extended into the desired ready-to-wear garment style. The garment block is obtained by using a virtual 3D-to-2D design method. The extension and sizing of the garment block pattern into desired ready-to-wear garment patterns is performed in a 2D environment using classic methods. The proposed design solution begins with a personalized garment block, thus avoiding the complicated operations of simulating a 3D garment directly in the virtual environment. The proposed design process can be fully digitalized, which ensures the involvement of the consumer throughout the design. By repeatedly running the sequence of Design – Display – Evaluation – Adjustment, which is technically accomplished through the virtual 3D-to-2D design method and 3D virtual try-on, the designers’ patterns and principles of elaborating personalized garment products can be validated within a very short time. As a knowledge-supported design process, designers’ design ideas and principles of personalized design solution can be fully extracted to enhance satisfaction of the final product. A set of experiments and case studies validated the approach and application of the proposed knowledge-supported virtual design process, and demonstrated its efficiency.