This study was carried out to investigate the virulence of both entomopathogenic nematode Steinernema riobravae and entomopathogenic fungi Beauveria bassiana against last larval instars of Galleria mellonella. Both pathogens were either applied individually and as a group by inoculation of nematode simultaneously or 2, 4 and 6 days post fungal infection. Moreover, the effect of fungal infection on the nematode's penetration ability and reproduction potential were also evaluated. The results indicated that by increasing pathogen concentrations the host mortality percentage increased. LC₅₀ values were 12.3 IJs/ larva for S. riobravae and 309.62conidia/ml for B. bassiana. The nematode's penetration ability was significantly reduced when nematode applied at 2, 4, and 6 days post fungal infection. A significant reduction in infective juveniles production was observed when nematode applied at 2 and 6 days post fungal infection. However, the combination of two pathogens increased the effectiveness of pest control, their development is affected possibly by competition for the host and the understanding of these interactions will make it possible to determine the compatibility of the components of biological control to be used.