Metallurgical factors influencing toughness of the Intercritically Reheated Coarse-Grained Heat Affected Zone (ICCG HAZ) of multiple welded SA508-cl.3 Reactor Pressure Vessel Steel were evaluated. The recrystallized austenite formed along the prior austenite grain boundaries and late interfaced on heating to the intercritical range was transformed to bainite and/or martensite during cooling. The newly formed martensite always included some retained austenite(M-A constituents). The characteristics(amount, hardness, density, and size) of M-A constituents were found to be strongly associated with both peak temperature and cooling time(△t8/5(2)) of last pass. Toughness in the ICCG HAZ was deteriorated with increasing amount of M-A constituents which was increased with increasing the last peak temperature within the intercritical temperature range. Meanwhile, for the same intercritical peak temperature, toughness was decreased with increasing cooling time. When cooling time was short, the dominant factor influencing toughness of the ICCG HAZ was amount of M-A constituents. However, when cooling time was lengthened, the hardness difference between M-A constituents and softened matrix(tempered martensite) was found to be the dominant factor.