A study was conducted to evaluate the effects of δ-aminolevulinic acid (ALA) on blood characteristics and immune organ weight in broilers. One-day-old broiler chicks were randomly assigned to one of four dietary treatments with six replicates of 20 chickens each. Treatments were basal diet supplemented with 0, 5, 10 and 15 mg/kg ALA. The two-phase experimental diets were formulated to meet the NRC requirements for chicks and fed for 5 weeks. Growth performance was not affected by supplementation of ALA during any of the experimental periods. Blood cell counts (WBC, RBC and lymphocyte), serum total protein, albumin, iron concentrations, and total iron binding capacity (TIBC) were also not influenced by dietary treatments. Haemoglobin concentration tended to increase with an increased ALA supplementation level (linear effect; P<0.10). Dietary ALA addition did not influence liver weight. However, spleen and bursa of fabricius weights were increased with the increased ALA supplementation level (linear effect; P<0.05). The current data indicate that supplementation of ALA in commercial broiler diets could partly improve haemoglobin concentration and immune organ weights, without influencing growth performance and other blood characteristics of broilers.