[Purpose] We previously searched for novel functions of chaperones and their binding proteins in the responses of human cells to UVC and reported that HSPs, including HSP27 and GRP78, and their binding proteins (HSP-binding proteins, HSPBs) play roles in protecting human cells against UVC lethality. Recently, HSPs and HSPBs have been suggested to be released into the extracellular space under stress exposure. In this study, we sought to confirm the involvement of extracellular HSPB-A, in cellular refractoriness to UVC-induced cell death in UVC-sensitive human cells. [Methods] Two human cell lines, UVC-sensitive RSa cells and Cockayne syndrome patient-derived (CS) cells, were used. Recombinant human HSPB-A (rHSPB-A) was added to the culture medium. After 24 h of culture in the presence of rHSPB-A, the cell survival capacities following UVC irradiation were analyzed by colony formation assays. The abilities of the cells to remove UVC-damaged DNA were evaluated using an antibody against damaged DNA. rHSPB-A was prepared by PreScission protease digestion of GST-fused HSPB-A. [Results and Conclusions] Preculture of RSa and CS cells in medium supplemented with rHSPB-A (0.5 μg/ml) enhanced the cellular refractoriness to UVC-induced cell death compared with mock cultured cells. In contrast, the sensitivities of the cells to X-rays or 5-FU were not remarkably modulated by the preculture. Cells precultured in rHSPB-A-supplemented medium did not show increased capacities to remove UVC-damaged DNA. These results suggest that extracellularly added HSPB-A confers resistance to UVC-induced cell death on human cells with high UVC sensitivity. Mechanisms other than the DNA repair process examined here, such as extracellular signal transduction, may be involved in the extracellular HSPB-A-associated UVC resistance.