This physical weld simulation study deals with the coarse grain heat-affected zone (CGHAZ) region's microstructure and the mechanical properties of naval bainitic steel after multi-pass welding. A welding thermal physical simulation experiment has been carried out by simulating different subzones (temperature range between 1100ý and 600 °C) in reheated coarse-grained heat-affected regions. The weld thermal cycles were tested between these temperature ranges using a thermo-mechanical simulator Gleeble®3800. The fixed low heat input 15 kJ/mm was used. The hardness, impact toughness at −50 °C, and notched tensile properties of the sub-CGHAZ regions were tested, and average results are reported. The altered CGHAZ microstructures were analyzed through optical microscopy, SEM, and TEM facility. This CGHAZ microstructure consisted of granular bainite, martensite, bainitic ferrite, and martensite austenite (M/A) islands, while base metal steel consisted of tempered bainite and martensite, and M/A islands. The first-pass CGHAZ region's mechanical properties were found worst due to coarse microstructure, whereas improved mechanical properties were obtained after the subsequent pass (second pass). The improvement in mechanical properties of sub-CGHAZ regions was attributed to the microstructure of soft granular bainite, shorter length and coarser width of bainitic ferrite, soft M/A islands, and carbides as well as changes in prior austenite grain size. The correlation between CGHAZ structure and mechanical properties is established in detail. © 2021, ASM International.