Hybrid electric vehicle (HEV) is one of the most highly pursued technologies for improving energy efficiency while reducing harmful emissions. Thermal modeling and control play an ever increasing role with HEV design and development for achieving the objective of improving efficiency, and as a result of additional thermal loading from electric powertrain components such as electric motor, motor controller and battery pack. Furthermore, the inherent dual powertrains require the design and analysis of not only the optimal operating temperatures but also control and energy management strategies to optimize the dynamic interactions among various components.This paper presents a complete development process and simulation results for an efficient modeling approach with integrated control strategy for the thermal management of plug-in HEV in parallel-through-the road (PTTR) architecture using a flexible-fuel engine running E85 and a battery pack as the energy storage system (ESS). While the main motivation for the work is to deliver a design for the Department of Energy's EcoCAR2 Plugging in to the Future Competition, yet the framework and methodologies should be useful for any typical hybrid powertrain thermal and control development.The frameworks of this project include simulating the thermal behavior of major HEV powertrain components using system oriented models more suitable for real-time vehicle operations. A comprehensive control algorithm is established in a Thermal Manager, as part of vehicle supervisory controller. Finally, the proposed model is tested through realistic driving conditions to demonstrate reliability.