Gastrointestinal parasites are responsible for high economic losses to sheep production. Infected animals show developmental problems, reduced weight and a low quality of meat and wool. This study takes into consideration two different sheep management systems, indoor (n = 50) and outdoor (n = 50) ones, and their impact on the occurrence of gastrointestinal parasites. Coproscopic examinations of sheep were made three times during one season. Flotation, sedimentation and McMaster methods were applied to determine the parasite species, prevalence of infection and mean EPG/OPG of parasites. Sheep from indoor management carried only 3 parasite taxa (Trichostrongylidae spp., Capillaria spp. and oocysts Eimeria spp.) whereas, 4 parasite taxa were derived from individuals kept in the outdoor management system (Trichostrongylidae spp., Nematodirus spp., Trichuris spp., and Moniezia spp). The overall prevalence of G.I. parasites was 3.4-fold higher in sheep from the outdoor management system. Sheep kept outdoors showed significantly higher overall mean EPG/OPG values for all taxa. Results of this study show that sheep kept outdoors are subject to intensive parasite invasions as compared to individuals managed indoors.