Enzymatic inhibition is one of the key regulatory mechanisms in cellular metabolism, especially enzymatic competitive inhibition by product. This inhibition process helps cells regulate enzymatic activities. In this paper, we derive a mathematical model describing enzymatic competitive inhibition by product. The model consists of a coupled system of nonlinear ordinary differential equations for the species of interest. Using nondimensionalization analysis, a formula for the product formation rate in this mechanism is obtained in a transparent manner. Further analysis of this formula yields qualitative insights into the maximal reaction velocity and the apparent Michaelis–Menten constant. By integrating the model numerically, the effects of the model parameters on the model output are also investigated. Finally, a potential application of the model to realistic enzymes is briefly discussed.