Although a great deal is known about the signaling events that promote nuclear translocation of NF‐κB, how cellular biophysics and the microenvironment might regulate the dynamics of this pathway is poorly understood. In this study, we used high‐content image analysis and Bayesian network modeling to ask whether cell shape and context features influence NF‐κB activation using the inherent variability present in unperturbed populations of breast tumor and non‐tumor cell lines. Cell–cell contact, cell and nuclear area, and protrusiveness all contributed to variability in NF‐κB localization in the absence and presence of TNFα. Higher levels of nuclear NF‐κB were associated with mesenchymal‐like versus epithelial‐like morphologies, and RhoA‐ROCK‐myosin II signaling was critical for mediating shape‐based differences in NF‐κB localization and oscillations. Thus, mechanical factors such as cell shape and the microenvironment can influence NF‐κB signaling and may in part explain how different phenotypic outcomes can arise from the same chemical cues.