Hydrogen trapping behavior of the subzones in the fusion welds of X52 pipeline and their associated hydrogen embrittlement (HE) susceptibility remains insufficiently understood, despite the wide use of this class of pipelines for high-pressure hydrogen transportation. In this study, the hydrogen concentration and the desorption characteristics of different sub-regions, including base metal (BM), heat-affected zone (HAZ), and weld zone (WZ) of X52 welds were analyzed using thermal desorption spectroscopy (TDS), while the HE susceptibility was evaluated through slow strain rate tensile (SSRT) test. Both electrochemical and high-pressure gaseous hydrogen charging conditions were compared. TDS analysis of the hydrogen charged samples reveals that most hydrogen resides in shallow traps with hydrogen binding energy less than 60 kJ/mol. The BM and HAZ contain reversible hydrogen traps (grain boundaries and dislocations) with a desorption peak near 100°C and irreversible traps (high-energy grain boundaries and precipitate interfaces) with desorption peaks at 350-450°C and even a peak near 700°C, which is related to TiC precipitates. However, the WZ exhibits two reversible hydrogen trap peaks near 100°C and an irreversible hydrogen trap in the 350–450°C range, while lacking the TiC deep traps. The HAZ region is more prone to crack initiation than the BM, and this is attributed to the higher ratio of reversible-to-irreversible hydrogen traps in HAZ, which is 4.14:1 whereas this ratio is 2.31:1 for BM, although the total hydrogen concentration in these two types of structure is similar under electrochemical hydrogen charging conditions. In addition to crack initiation on the external surfaces, initiation at internal microstructural weak sites such as martensite-austenite (M-A) constituents and precipitates, can also occur, causing significant brittle transgranular cracking in the surrounding areas. This is observed under electrochemical charging condition which produced severe HE effects with susceptibility index (IH ) of 79.05%. However, this phenomenon is not observed under 6.3 MPa gaseous hydrogen charging, where the total hydrogen in the sample is lower by about 45%, with a much lower susceptibility index (IH ) of 8.01%.