The consumption of n-3 PUFAs is low, particularly the long chain (>18 carbon atoms) fatty acids that are most commonly found in fish oils. These dietary fatty acids have been shown to have a great effect on the health and immune status of different species including humans, rats and poultry. The current paper reviews studies on the effect of dietary polyunsaturated fatty acids on B- and T-cell subpopulations in peripheral blood, spleen, and thymus of poultry.