β-glucan (Macrogard®) was administrated to enhance the immunity and growth of Cyprinus carpio fry. The whole body homogenate of fish sampled with one week intervals during 2nd - 6th weeks post hatching was assayed for the total protein content, lysozyme activity, α-2-macroglobulin content, classical complement pathway activation, and weight gain. After the 3rd week of experimental feeding, the total protein content and the classical complement activity of fish fed β-glucan supplemented diet were higher than controls. Significantly higher lysozyme activity and α-2-macroglobulin levels were noted in group fed β-glucan at the 2nd and 3rd week of diet application. It was demonstrated that β-glucan enriched feeding increased the immunity of common carp at the earliest stages of their development.