Necrotic enteritis (NE) and gangrenous dermatitis (GD) are important infectious diseases of poultry. Although NE and GD share a common pathogen, Clostridium perfringens, they differ in other important aspects such as clinical signs, pathologic symptoms, and age of onset. The primary virulence factors of C. perfringens are its four major toxins (α, β, ε, ι;) and the newly described NE B-like (NetB) toxin. While neutralizing antibodies against some C. perfringens toxins are associated with protection against infection in mammals, the serologic responses of NE- and GD-afflicted birds to these toxins have not been evaluated. Therefore, we measured serum antibody levels to C. perfringens α-toxin and NetB toxin in commercial birds from field outbreaks of NE and GD using recombinant toxin-based enzyme-linked immunosorbent assay (ELISA). Initially, we used this ELISA system to detect antibody titers against C. perfringens α-toxin and NetB toxin that were increased in birds experimentally co-infected with Eimeria maxima and C. perfringens compared with uninfected controls. Next, we applied this ELISA to field serum samples from flock-mated birds with or without clinical signs of NE or GD. The results showed that the levels of antibodies against both toxins were significantly higher in apparently healthy chickens compared to birds with clinical signs of NE or GD, suggesting that these antitoxin antibodies may play a role in protection against NE and GD.