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Post-irradiation annealing (PIA) was conducted on a 304L stainless steel irradiated to 5.9 dpa in the Barsebäck-1 boiling water reactor (BWR), to investigate its effect on the irradiated microstructure and the mitigation of irradiation-assisted stress corrosion cracking (IASCC) susceptibility. Evolution of irradiated microstructure including faulted dislocation loops, radiation-induced solute clusters and radiation-induced segregation (RIS) at the grain boundary was investigated in the as-irradiated condition and following thermal annealing at 500°C and 550°C for times up to 20 h. IASCC susceptibility was measured for the as-irradiated and four PIA conditions (500°C: 1 h and 550°C: 1, 5, and 20 h) via interrupted constant extension rate tensile and four-point bend experiments under simulated BWR normal water chemistry (NWC) conditions. While the faulted dislocation loop size did not change significantly after annealing up to 550°C: 5 h, the loop number density decreased steadily with increased annealing treatments, and faulted loops were fully removed after annealing at 550°C: 20 h. The average size of Ni-Si and Al-Cu clusters increased while the number density decreased with increased annealing. RIS of various elements progressively decreased with extent of annealing but were not fully removed by 550°C: 20 h. The annealing treatments were also observed to progressively reduce IASCC susceptibility, as measured by the final intergranular fracture fraction (tensile) and crack length per unit area (four-point bend), with full removal of IASCC susceptibility being observed following annealing at 550°C: 1 h for tensile specimens and 500°C: 1h for four-point bend specimens. Among the microstructure and mechanical property parameters measured as a function of PIA, the changes in the average dislocation channel spacing was observed to most closely relate to the mitigation of IASCC; decreasing by ~25% and ~40% from the as-irradiated condition after annealing at 500°C: 1 h and 550°C: 1 h, respectively. The mitigation of IASCC susceptibility correlated well with the decrease in the average dislocation channel spacing and is consistent with a process in which crack initiation is controlled in part by the high normal stress at discontinuous dislocation channel-grain boundary intersections.