BACKGROUNDThe gut microbiota has an intimate relationship with insect hosts and this relationship can become complicated with parasitic organisms being involved with the host. To date there has been limited evidence for the relevance of parasitism of the host by parasitoids to host gut microbiota, especially in host insect predators. Here, our study examined gut microbiotas in larvae of the predaceous lady beetle, Coccinella septempunctata, in response to their parasitism by Homalotylus eytelweinii regarding the development progress of offspring parasitoids.RESULTSOverall 58.5% of gut bacterial operational taxonomic units (OTUs) in the parasitized lady beetle were different from those in the unparasitized host. The phylum Proteobacteria abundance increased while Firmicutes decreased in parasitized hosts compared to the unparasitized. The abundance of genus Aeribacillus decreased substantially in the parasitized lady beetle across all stages of the offspring development compared to the unparasitized host. The α‐diversity of the gut microbiota in a parasitized lady beetle larva increased at the early stage of offspring parasitoids and then returned over the intermediate and later stages. Analyses of β‐diversity indicated that the gut microbial community in a parasitized lady beetle was distinct from that in an unparasitized one and different between early or middle and late stages of offspring parasitoids in parasitized hosts.CONCLUSIONOur results provide evidence for the relevance of the gut microbiota to interactions between a lady beetle host and its parasitoid. Our study provides a starting point for further investigations of the role the gut microbiota may play in host‐parasitoid interactions. © 2023 Society of Chemical Industry.