The cracking behavior of reactor core internal materials is a key factor for the long-term safety and availability of light water reactors. Subject to corrosive coolant, thermal and mechanical loading, and neutron irradiation, reactor core internal materials are susceptible to several degradation mechanisms during power operation. To understand the long-term effects of neutron irradiation, baffle-plate materials harvested from a decommissioned pressurized water reactor have been evaluated for cracking susceptibility and fracture resistance at different doses. Small compact-tension specimens were machined from different locations on the baffle-plate assembly with irradiation doses ranging from 0.06 to 48 dpa. Crack growth rate and fracture toughness J-R curve tests were performed on these specimens in simulated light water reactor environment, and the fracture morphologies of the tested samples were examined. While no elevated cracking susceptibility was observed for some samples tested in the low-corrosion-potential environment, a rapid cracking behavior featuring high crack growth rates was observed in some high-dose samples at elevated stress intensity factors. The fracture resistance of the decommissioned material declined considerably with the increasing neutron irradiation, leading to severe irradiation embrittlement at high doses. The severe embrittlement experienced by this baffle-plate material may be related to the rapid cracking response in the SCC tests.