The primary purpose of the dissertation research was to explore 3D digital prototyping through the development process of compression sportswear. Through this purpose, the study proposed a novel method of how 3D digital prototyping could be applied in developing advanced compression sportswear design and examined the wear comfort of commercial compression tops compared to a novel design developed for the study. Also, the study examined the validity of 3D digital prototypes in contrast to the actual prototypes of the novel design in terms of static and dynamic fit conditions. Additionally, the study tested the latest soft avatars with fit appearances and measurements compared with rigid avatars and actual fit.This study adopted comprehensive research methods to create and investigate 3D digital design using the latest technologies, such as 3D body scans, 3D virtual simulation, and 3D virtual animation. The study was divided into three study phases: (1) developing a novel design of women’s compressive tops by consumer research, interviewing with technical designers, 3D digital prototyping, and human subject tests; (2) examining the validity of 3D digital prototyping; and (3) investigating fit appearances and measurements on 3D soft avatars. In the first study phase from the consumer research of survey data collection, it was found that women wanted to have intensive pressure at the abdomen and waist for compression tops in strength training. Technical designers indicated that they prefer working with live fit models when designing compression sportswear. Therefore, a need to validate the usefulness of 3D digital prototyping in compression sportswear development was identified. Prototypes of a novel compression top design were developed through a series of experimental procedures of user tests with commercial products, 3D-to-2D flattened prototype patterns, digital pressure measurements, and strain maps for fabric stretch rates. Compared to control tops, the prototypes were evaluated in terms of wear comfort in perceived pressure levels and duration of athletic performances in user tests. In the second study phase, virtual and actual fit were compared in static and dynamic settings. The virtual prototypes were found to be significantly longer in top lengths at front, back, and side and significantly larger at the waist cross-sectional areas on rigid avatars compared to the actual prototypes, but this finding was not statistically significant in top length comparisons in another virtual software. Shoulder shapes in the virtual prototypes were distorted differently from the actual prototypes in dynamic fit, which caused measurement differences as well. In the third study phase, it was found that the soft avatars reacted to garment pressure, particularly at the breast. The fit appearance at the breast presented a more rounded shape than a rigid avatar, while the garment pressed the bust area. This fit appearance was similar to the actual fit. The present study provided useful ideas on how 3D digital prototyping can be applied in the development of advanced compression sportswear. Also, the study guided what aspects should be improved to better animate 3D virtual garments similar to actual garments in static and dynamic conditions.