Probiotics are of great practical importance in animal husbandry and veterinary medicine. However, at times, putting them into operation is fraught with difficulties caused by unexpected side effects. This is often due to the selection of an inappropriate model organism when testing probiotics. The model organism must meet a number of requirements, and at the same time be convenient for use. One of the models widely used at the moment is based on nematodes. Caenorhabditis elegans is currently being used as a model organism to study host-bacteria interactions in the gut and the general effect of probiotics on the host organism. On nematodes, one-time studies of a particular group of potentially suitable probiotics can be carried out. And nematodes can also be considered quite convenient organisms to be used as test systems for a wide range of probiotics. Nematodes have a number of advantages over other model organisms, however, they are also limited in use, so they have not yet ousted their competitors. Here, we will show the features and consider the pros and cons of this model host for probiotic studies.