The aim of this study was to assess and validate the herbal anthelmintic remedies used by farmers in Kirinyaga county, Kenya for the treatment of their cattle against gastrointestinal nematodes. The herbs used were identified via questionnaire surveys through focused group discussions. The aqueous extracts of plants used: Aspillia pluriseta, Vernonia lasiopus, Entada leptostachya and Erythrina abyssinica were prepared and using dosage between 10 and 30%, the viability of infective strongyle larvae were assessed for a period of 48 h. The results of the in vitro antihelmintic study indicated a high to moderate anthelmintic activity for the tested extracts. E. leptostachya exhibited the highest in vitro anthelmintic activity, while E. abyssinica had the lowest activity. The anthelmintic activity may have been due to the presence of saponins in the herbal remedies. There was a positive correlation between the saponin concentration and the anthelmintic activity of the extracts. In general, the in vitro anthelmintic activity increased with the extract concentration for the medicinal plants examined.