A two-fluid one-dimensional model has been developed to predict the wall temperature of an internally heated tube during inverted annular flow film boiling (IAFB). The model is derived using basic conservation equations of mass, momentum, and energy. To simplify the derivation of the constitutive heat transfer relations, flow between two parallel plates is assumed. The model features shear stress and interfacial relations that make it accurately predict the parametric effects and heat transfer characteristics of IAFB over a wide range of flow conditions. The model predicts wall temperatures of R-134a-cooled tubes with an average error of and a rms error of 6.37%. This corresponds to average and rms errors in predicted heat transfer coefficients of 1.33% and 10.07%, respectively. Using water data, the model predicts wall temperatures with an average error of and a rms error of 7.78%, which corresponds to average and rms errors in predicted heat transfer coefficients of 4.16% and 15.06%, respectively.