Generalist parasitoid wasps possess the capacity to parasitize multiple host species in their native habitats. When invasive pests encroach into their habitat ecosystems, these native parasitoids may expand their host range by incorporating the novel invaders as viable host resources. A prominent example is the native Chinese pupal parasitoid Chouioia cunea, which has successfully utilized the invasive fall webworm (Hyphantria cunea) as a novel host. However, not all generalist parasitoids exhibit this adaptive capability, as the exploitation of novel hosts requires fulfillment of specific ecological and physiological criteria. Based on global case studies of parasitoid-host expansion, this review synthesizes critical factors influencing parasitoids’capacity to adopt novel hosts. The first important factor is temporal and spatial synchrony. The foundational prerequisite for establishing a parasitoid-host relationship is the temporal overlap between the oviposition period of maternal parasitoids and the developmental stage of the novel host suitable for parasitism. Additionally, the novel host’s habitat during this vulnerable stage must align ecologically with that of the original host. For instance, synchrony in phenology ensures that emerging parasitoid offspring encounter hosts at susceptible life stages. The second factor is host-induced plant volatiles (HIPVs). When novel and original hosts infest the same plant species, the plant-derived volatile organic compounds (VOCs) emitted in response to herbivory must elicit analogous attraction in parasitoids. These HIPVs serve as indirect cues for host location. Cross-species recognition of these chemical signals is essential for parasitoids to associate novel hosts with familiar foraging environments. The third factor is host-location mechanisms. Successful parasitoids must either (i) utilize conserved semiochemicals (e.g., kairomones) shared between original and novel hosts for precise localization or (ii) recognize functionally equivalent volatile compounds from novel hosts, even if structurally distinct from those of original hosts. This dual mechanism ensures that parasitoids bypass structural variability in host-derived cues while retaining chemosensory efficacy. The fourth factor is morphological compatibility. The physical architecture of the novel host during its parasitism-susceptible stage must resemble that of the original host. Similarities in body size, cuticle thickness, or defensive structures facilitate parasitoid acceptance, ovipositor penetration, and egg deposition. Morphological mismatches often lead to rejection or failed parasitism. The last factor is nutritional suitability. Post-oviposition, the novel host’s internal physiological environment must support the complete development of parasitoid offspring. This includes compatibility with host hemolymph composition, immune evasion mechanisms, and nutrient availability. For instance, host-specific immune responses or inadequate nutrient profiles may disrupt larval development, precluding adult emergence. These factors combine provide a framework for screening and harnessing native parasitoids to combat invasive pests through classical or augmentative biological control. By prioritizing parasitoids that meet these factors, practitioners can enhance the success rate of biocontrol programs while minimizing non-target effects. The case of Chouioia cunea exemplifies how understanding host-switching mechanisms enables targeted deployment of natural enemies against invasive species, offering sustainable solutions to ecological invasions.