This paper introduces thermodynamic and economic analyses on a newly developed energy system for powering hybrid vehicles based on both energy and exergy concepts. The proposed hybrid propulsion system incorporates a liquefied ammonia tank, ammonia dissociation and separation unit (DSU), an internal combustion engine (ICE), and a fuel cell (FC) system. The exhaust gases released from the ICE are exploited to supply the necessary thermal energy to decompose ammonia thermally into hydrogen and nitrogen on board. The ICE is fuelled with a blend of ammonia and hydrogen generated from the DSU. The additional hydrogen released from the DSU will also be provided to the fuel cell system to run the FC and generate electric power, which will be supplied to the electric motor to provide the required traction to the vehicle. An optimization study is also performed to identify optimum design variables. The parametric studies are included in this investigation to evaluate the influence of varying the different operational parameters on the system energy and exergy efficiencies and both total cost rate and exergoeconomic factor values of the system. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.