Physical interactions between two immune cells or between immune and cancer cells play a major role in shaping the immune response in the tumor microenvironment, making them prime therapeutic targets for bispecific engagers. Here, we present a protocol for assessing murine cell doublet engagement and subsequent effects using flow cytometry and imaging flow cytometry. We describe steps for identifying bispecific cell engager antibodies at the cell-cell interface, doublet quantification, and characterizing cellular protein morphology and processes within the doublet. For complete details on the use and execution of this protocol, please refer to Shapir Itai et al. 1 .