This paper presents numerical modeling and structural analysis of a 75-year-old masonry head regulator constructed on an irrigation canal in Egypt. Numerical modeling by finite elements and nonlinear analysis are carried out using commercial software ANSYS. The finite element model represents the current condition including characterization of the deteriorated material properties. Nonlinear analysis is conducted to evaluate the structural behavior under the applied and the worse expected loading condition to assess its structural efficiency and safety margin and strengthening requirements. The result of the numerical modeling for the regulator are presented and discussed in terms of compression and tensile stresses and deformations of the structure.