During phagocytosis, surface receptors on neutrophils interact with pathogens opsonized with complement factor C3b/iC3b and in some cases with antibodies. In human immune sera antibodies directed against surface‐bound M proteins mediated killing of Streptococcus pyogenes by neutrophils. Surprisingly, blocking of the Fc receptors had little effect on the killing. In contrast, inhibition of C3b/iC3b generation, or blocking of the major neutrophil iC3b receptor CD11b/CD18, enabled S. pyogenes to grow efficiently in immune sera. Inhibition of CD11b/CD18, but not of CD32, the major neutrophil signaling Fc receptor, prevented Streptococcus‐induced NADPH oxidase‐dependent respiratory burst, and blocking of C3b/iC3b formation inhibited Streptococcus‐induced activation of Cdc42, a small GTPase critically involved in transmitting pro‐inflammatory signals to the cytoskeleton. Consequently, ligation of CD11b/CD18 by bacteria‐bound iC3b is necessary for inducing a neutrophil response leading to elimination of S. pyogenes in immune human serum.