Nonspecific inflammation is associated with primary graft nonfunction (PNF). Inflammatory islet damage is mediated at least partially by pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) produced by resident islet macrophages. The p38 pathway is known to be involved in cytokine production in the cells of the monocyte–macrophage lineage. Therefore, inhibition of the p38 pathway may prevent pro-inflammatory cytokine production by resident islet macrophages and possibly reduce the incidence of PNF. Our present study has demonstrated that inhibition of the p38 pathway by a chemical p38 inhibitor, SB203580, suppresses IL-1β and TNF-α production in human islets exposed to lipopolysaccharide (LPS) and/or inflammatory cytokines. Although IL-1β is predominantly produced by resident macrophages, ductal cells and islet vascular endothelial cells were found to be another cellular source of IL-1β in isolated human islets. SB203580 also inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the treated islets. Furthermore, human islets treated with SB203580 for 1 h prior to transplantation showed significantly improved graft function. These results suggest that inhibition of the p38 pathway may become a new therapeutic strategy to improve graft survival in clinical islet transplantation.