An experiment was conducted to determine the effects of two different water-soluble carbohydrate extracts (renga renga lily extract and 'Acacia' extract), and two commercially available prebiotic compounds, Fibregum and Raftifeed-IPE, on the performance of broiler chickens subjected to a necrotic enteritis (NE) challenge model. These treatments were compared with negative control and a positive (Zn-bacitracin) control treatments. An overall 8.8% NE-related mortality was recorded, with mean jejunal and ileal lesion scores in dead birds ranging from 3.03 to 3.90 in all challenged groups except the positive control groups. NE-specific deaths or clinical abnormalities were not observed with unchallenged control and positive control groups. At 7 days post-challenge, the concentration of specific IgY antibodies against the α-toxin of 'Clostridium perfringens' in the serum was lower ('P' < 0.05) in birds fed the positive control and Fibregum-supplemented diets than in the negative control group. However, birds fed Fibregum had increased ('P' < 0.05) IgM concentration compared with those fed 'Acacia' extract and lily extract. The Fibregum-fed group also had higher ('P' < 0.05) IgA concentrations in serum than did the positive-control and lily extract-supplemented groups at 14 days but this effect did not persist to 21 days. The results from the present study demonstrated that supplementation with water-soluble carbohydrates from two plant sources was not effective in controlling NE. However, the prebiotic compound Fibregum was found to be having some immunomodulatory effects. Addition of Zn-bacitracin and monensin was highly effective in counteracting the negative effects of the disease challenge.