This article proposes an approach to a hybrid software process simulation modeling (SPSM) using discrete event system specification (DEVS) formalism, which implements the dynamic structure and discrete characteristics of the software development process. Many previous researchers on hybrid SPSM have described both discrete and continuous aspects of the software development process to provide more realistic simulation models. The existing hybrid models, however, have not fully implemented the feedback loop mechanism of the system dynamics. We define the DEVS_Hybrid_SPSM formalism by extending DEVS to the hybrid SPSM domain. Our hybrid SPSM approach uses system dynamics modeling to convey details concerning activity behaviors and managerial policies, while discrete event modeling controls activity start/completion and sequence. This approach also provides a clear specification, an explicit extension point to extend the simulation model, and a reuse mechanism. We will demonstrate a Waterfall-like hybrid software process simulation model using the DEVS_Hybrid_SPSM formalism. Copyright ？ 2006 John Wiley & Sons, Ltd.