Cases of rumen impaction caused by ingestion of Gonometa postica cocoons occurred at a farm in eastern-central Namibia. Ten animals died on the farm over the previous 5 months. Rumenotomies were successfully performed on three affected animals. The authors were of the opinion that the affected animals ingested the cocoons around the time of weaning, which then resulted in tangled masses that gradually stretched and enlarged because of entrapment of ingesta, eventually causing impaction of the rumen in the young adult animals. These are the first reported cases of ruminal impaction attributable to G. postica cocoon ingestion in Namibia.