The control strategy of a hybrid electric vehicle (HEV) is generally not disclosed to public because it is a significant factor in determining the performance of the system. However, engineers desiring to understand the control concept of real-world HEVs can gain knowledge in various ways. In this study, we used test data obtained from a bench dynamometer and real driving to analyze the supervisory control strategy of Hyundai Ioniq Hybrid. This research can be described in three steps. First, an understanding of the mode control strategy is obtained by investigating the engine on/off behavior, which determines when the pure electric driving mode is used. Second, the shifting patterns are studied by observing the speed ratios according to the vehicle speed and the torque demand. Third, the strategy for distributing the torque between the engine and the motor is analyzed by studying the motor assistant operation. Based on the analyzed control concept, it is possible to understand the technical strategy for improving the fuel efficiency of the parallel hybrid system. This study would be useful for engineers who want to design controllers for HEVs, in that it provides the analyzed control concept and the real-world operating behaviors.