Gas-assisted injection molding is an innovative process that can provide tremendous flexibility in design and manufacturing of plastics parts once it is fully understood and matured. The research effort presented in this article is aimed at development of Computer-Aided Engineering (CAE) technology for gas-assisted injection molding. To achieve the goal, efforts have been made in developing a numerical analysis for predicting the filling and post-filling behavior and verifying the predictions through collaboration with the industry and universities. This article firstly describes the physics of this process, which leads to the various advantages and the inherent difficulties associated with the design and processing. Secondly, it discusses the methodology of numerically modeling and simulating gas-assisted injection molding filling dynamics together with experimental comparison. At the end of this article, it presents the various advantages of applying the CAE technology for the gas-assisted injection molding process, such as evaluating the various gas-assisted injection molding processes and establishing preliminary design guidelines.