A chemical and microbiological characterization on Hermetia illucens larvae was carried out as well as an inactivation study of natural contaminating microorganisms and inoculated E. coli O157:H7 in black soldier larvae by using High Hydrostatic Pressure (250 to 400 MPa, for 1.5 to 15 min). Hermetia illucens was mainly composed of proteins (46.49%, d.m.) followed by fat (37.88%, d.m.). Larvae had a high contamination load of Total Aerobic Mesophilic bacteria (AMB) (1.58x107 cfu/g) and Enterobacteriaceae (1.15x106cfu/g). The presence of pathogenic microorganism varied: no Listeria spp. were found, but Salmonella (1.15x106 cfu/g) and E. coli (7.08x105 cfu/g) were detected in the larvae extract. High Hydrostatic Pressure (HHP) was effective against natural contaminating yeasts and molds producing more than 5 log cycle reductions at 400 MPa for any of the times considered (2.5 to 7 min), but a low reduction of total microbial load was achieved. The inactivation level of larvae inoculated with E. coli O157:H7 varied. At 400 MPa for 7 min more than 5 log cycle reductions were achieved. Among the three inactivation models studied, the one that best described the inactivation pattern of the cells, according to the Akaike index, was the Biphasic model.