The aim of this study was to determine the influence of the environmental enrichment and the animal density in cage on some welfare parameters in male Swiss albino mice. The experiment was conducted as a 3 [three housing conditions: Non-enriched, enriched with a nest box and super-enriched with a nest box and cotton] X 2 [two animal densities: 2 or 5 mice per cage] full factorial design on 126 male, 8 week old, mice for 12 weeks. Body weights, weight gains and food intake were weekly measured, the behaviour was estimated by the cage emergence test on 18 week old mice, the serum corticosterone concentrations, the titres of the circulating anti-sheep erythrocyte antibodies induced after experimental immunisation and the relative weights of the adrenal gland, the spleen and the thymus were determined at the end of the experiment. Whereas the housing conditions have not significantly affected the weight gain, the circulating corticosterone and antibody concentrations and the relative weight of organs, the environmental enrichment and the cage crowding have significantly reduced the food intake. In addition, the cage escape duration was significantly decreased in mice reared in enriched and super-enriched environments. These results indicate that the improved housing conditions compared to the normal conditions have directly influenced the food intake and the mouse behaviour without interfering with the stress and immune responses.