<b><i>Background:</i></b> Genetic variations contribute to septic shock mortality. To discover a novel locus, we performed in vitro genome-wide association studies (GWAS) and further tested the result in a cohort of septic shock patients. <b><i>Methods:</i></b> Two in vitro GWAS using a quantitative trait locus analysis of stimulated IL-6 production in lymphoblastoid cells from 60 individuals of European ancestry were performed. <i>VPS13D</i> rs6685273 was genotyped in European ancestry patients (n = 498). The <i>VPS13D</i> gene was silenced in vitro. <b><i>Results:</i></b> Two GWAS using lymphoblastoid cells identified the locus of <i>VPS13D</i> rs6685273 that was significant in the same direction in both GWAS. The <i>VPS13D</i> rs6685273 C allele was associated with increased IL-6 production. Patients with septic shock who had the <i>VPS13D</i> rs6685273 CC genotype had an increased 28-day mortality (p = 0.023) and more organ failure (p < 0.05) compared to the CT/TT genotypes. <i>VPS13D</i> in vitro gene silencing in the HeLa cell line increased IL-6 production. Furthermore, the rs6685273 genotype was associated with differential <i>VPS13D</i> splice variant expression. <b><i>Conclusions:</i></b> The <i>VPS13D </i>rs6685273 C allele was associated with increased IL-6 production in vitro. The patients with the <i>VPS13D </i>rs6685273 CC genotype had increased 28-day mortality and increased organ failure. <i>VPS13D</i> appears to regulate IL-6 production.