The type VIIb secretion system (T7SSb) is a multisubunit protein export machine found in Gram-positive Firmicute bacteria which plays a key role in interbacterial competition. The T7SSb secretes a variety of toxic effector proteins targeting closely related strains, however the mechanism of secretion and the roles of numerous conserved genes within T7SSb gene clusters remain unknown. EsaD is a nuclease toxin secreted by the Staphylococcus aureus T7SSb, which forms a pre-secretion complex with its cognate immunity protein, EsaG, and chaperone EsaE. Encoded upstream of EsaD are three small secreted proteins of unknown function, EsxB, EsxC and EsxD. Here we show that these three proteins bind to EsaD and function as EsaD export factors and we report the first structural information for a complete T7SSb substrate pre-secretion complex. Cryo-EM of the EsaDEG trimer and the EsaDEG-EsxBCD hexamer shows that incorporation of EsxBCD confers an elongated conformation comprising a flexible globular cargo domain attached to a long narrow shaft that is likely to be crucial for efficient toxin export.