High strength tempered martensite steels are the primary choice for structural components, landing gear material as well as fastener components in automotive and aerospace industries. But these materials fail prematurely under service conditions due to Hydrogen Embrittlement (HE) leading to the total loss of integrity of structures. Therefore, in the present study, an approach was made to understand HE failure of two different steel grades in relation to susceptibility based on some simplifications of ASTM F1624-00 standard test method. As per, incremental step load (ISL) test results in 3.5wt% NaCl (Environmental Hydrogen Embrittlement (EHE)) environmental conditions, the steel grade having low Mo and S reveals better mechanical behavior as compared to the high Mo and S content one. Detailed fracture surface mapping revealed that intergranularity increases with increasing the potential of charging hydrogen against a comparatively ductile morphology when tested in air. The low Mo and S content steel showed lower intergranularity as compared to the high Mo and S one. Microstructural characterizations using Scanning Electron Microscopy (SEM), Electron Backscattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM) were performed to evaluate the potential trap sites of hydrogen like precipitates, dislocations and inclusions to correlate structure with the mechanical property test results and fractography. The ISL testing method has been further simulated using a finite element analysis (FEA) model to determine the hydrogen concentration profile in the notched bar specimens during the testing. The COMSOL Multiphysics® Modeling software has been used to develop the model in order to perform the stress coupled diffusion study in these materials. The FEA study further helps to explain the role of potential trap sites (from microstructural study) in influencing the susceptibility of these materials. Finally, a direct hydrogen quantification study was also performed using Thermal Desorption Spectroscopy (TDS) to further establish the above-mentioned results.