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Animals face both external and internal dangers: pathogens threaten from the environment, and unstable genomic elements threaten from within. Previously, we discovered thatC. elegansprotects itself from pathogens by “reading” bacterial small RNAs and using this information to both induce avoidance and transmit memories for several generations. Here we found that these memories can be transferred to naïve animals viaCer1retrotransposon-encoded capsids.Cer1functions at the step of transmission of information from the germline to neurons, and is required forC. elegans’learned avoidance ability and for mothers to pass this information on to progeny. The presence of theCer1retrotransposon in wildC. elegansstrains correlates with the ability to learn and inherit small RNA-induced pathogen avoidance. Together, these results suggest thatC. eleganshas co-opted a potentially dangerous retrotransposon to instead protect itself and its progeny from a common pathogen through its inter-tissue signaling ability, hijacking this genomic element for its own adaptive immunity benefit.