Strongyloides papillosus Wedl, 1856 is one of the most widespread nematodes parasitic in domestic animals. This species has been recorded on almost all continents of the planet. It parasitizes the small intestine of rabbits, sheep and cattle. At laboratory conditions, this species can also infect guinea pigs. Morphological variability of S. papillosus in relation to host species has not yet been studied. Our research showed that L1 and L2 of S. papillosus reached their maximum size in all parameters in guinea pigs: for L1 — length and width of the body, length of esophagus and intestine; for L2 — width of body and length of intestine. L3 of S. papillosus had statistically reliable differences in almost all parameters (except the length of intestine) when parasitizing goats and rabbits. For L3 the width of the body and the length of the tail end, we determined differences between S. papillosus infecting rabbits and guinea pigs, and also goats and guinea pigs. Male S. papillosus were observed to have statistically reliable differences in all morphological parameters for goats and rabbits, and also for rabbits and guinea pigs. Practically all measurements (except the length of the tail) were larger for S. papillosus in guinea pigs and goats than those in rabbits. Free-living females statistically differed by larger size in goats and rabbits. The smallest dimensions were determined for all free-living stages of S. papillosus in goats (except males). The largest size in most cases was determined for larval stages of S. papillosus in guinea pigs.