In order to minimize weight and provide redundancy, multi-cellular concrete box sections are typically utilized as the deck and pier systems of medium to long span bridges. Utilization of such sections has gained popularity in bridge construction since the mid-1980s. Nevertheless, extensive cracking in the walls of multi-cellular segmental concrete bridges has been discovered historically. This highlights the importance of better understanding the behavior of such complex members. Specifically, for resisting shear in an efficient manner, an understanding of the principles and methods used to perform a shear stress analysis on multi-cellular sections is warranted. Furthermore, structural/bridge engineers often feel frustrated as the techniques for performing this analysis are not readily available in the literature. The primary objective of this article is to provide practicing engineers with a working knowledge of the subject as well as the tools necessary to perform a shear analysis of multi-cellular box sections. This paper focuses on the distribution of shear stress throughout the walls of multi-cellular boxes. A rational and simplified analytical approach for determining this distribution in prismatic multi-cellular box sections is presented and discussed.