Pupal parasitoids are released as biocontrol agents against house flies and stable flies in livestock production systems, and entomopathogenic fungi may be compatible with the parasitoids. However, little is known on the dynamic interactions between pupal parasitoids and entomopathogenic fungi when based on releases of both biological control agents. Therefore, the compatibility of the pupal parasitoid Spalangia cameroni Perkins and the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin was examined in laboratory experiments. As a first step in this study, the susceptibility of S. cameroni to fungus infection was examined in a dose-response experiment, which was followed by a study on the effect of M. anisopliae on female survival and reproduction. The female parasitoids were moderately susceptible to M. anisopliae, with an LC₅₀ value 6 d after treatment of 2.97 × 10⁷ conidia/ml. When previously infected S. cameroni were provided with surplus fly puparia, no overall effect of fungal treatment on reproduction was found, although treatments with 1 × 10⁸ conidia/ml resulted in 50% infected individuals. The fungus infection significantly reduced the survival of the females, while the total fecundity (86.26 ± 8.63 progeny per female) was not statistically different from that of uninfected parasitoids (95.23 ± 6.88 progeny per female). As a result, the susceptibility of the parasitoids to fungal infection had no discernible effect on the intrinsic rate of natural increase (r_m). This strongly suggests that the isolate of M. anisopliae and S. cameroni could be compatible under field conditions. The results are discussed in relation to integrated fly control by combined use of S. cameroni and hyphomycetous fungi.