Theory of Constraints (TOC) is a new concept of overhaul management in power generation. It has been effectively used in various industrial activities. This paper describes the idea of how the TOC is applicable to improve the overhaul management dealing with several constraints with a case of power plant overhaul performance. TOC uses all five application tools to analyze a system or situation to identify a core problem, develop a solution for it, and determine how to implement that solution. These applications are CRT (Current Reality Tree), EC (Evaporating Cloud), FRT (Future Reality Tree), PRT (Prerequisite Tree), and TT (Transition Tree). The result of the study has shown several main factors causing the achievement of power generation overhaul performance not optimum. Based on the main causes that have been identified, it will give also some recommendations for improving the power generation overhaul performance such as personnel competencies acceleration and overhaul management process strengthened.