3D interactive simulation is important in human-computer interaction (HCI). In this study, we examined whether the technology is suitable for designing customized garments and the production process. We also investigated the virtual co-design behavior of users for a tailor-made garment design system. A task-technology fit (TTF) model was used for the system considering perceived risk factors. The system allowed for individual garment customizing for uniqueness and enjoyment. 408 responses for the 3D interactive garment tailor-made system were collected. For the evaluation of the model, we employed partial least squares (PLS) and structural equation modeling (SEM) for evaluation. The results confirmed that technology characteristics and the uniqueness and enjoyment of the system were related to TTF. However, clothing fitting was not a significant predictor of TTF. More than 60% (R 2 =0.663) of the variability in the continuance intention to adopt the system was obtained. In order to understand the substantive impact and predictive accuracy, we assessed effect size f 2 and predictive relevance q 2 . TTF had a medium effect size (f 2 =0.142) on the system usage intention, while perceived risk had a small effect size (f 2 =0.030). The findings also revealed that TTF had a small to medium degree of predictive relevance (q 2 =0.095) on usage intention, and perceived risk had a small degree (q 2 =0.020). The 3D interactive garment tailor-made system met users’ task demands and reduced users’ perceived risks. It is necessary to enhance 3D multimedia illustrations and improve body measurement techniques by adding more options and fun to the co-design process. The system contributes to the development of tailor-made systems.