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Aims:  Clostridium perfringens type A causes both clinical and subclinical forms of necrotic enteritis in domestic avian species. In this study the inhibitory effect of hen egg white lysozyme on the vegetative form of Cl. perfringens type A and the production of α‐toxin in vitro was investigated. Methods and Results:  A micro‐broth dilution assay was used to evaluate the minimal inhibitory concentrations (MIC) of lysozyme against three clinical isolates of Cl. perfringens type A in 96‐well microtitre plates. The MIC of lysozyme against Cl. perfringens isolates was found to be 156 μg ml−1. Scanning electron micrographs of the cells treated with 100 μg ml−1 of lysozyme revealed extensive cell wall damage. A quantitative sandwich ELISA for α‐toxin produced by Cl. perfringens was developed based on a commercial ELISA kit allowing only qualitative detection. Addition of 50 μg ml−1 of lysozyme did not inhibit the growth of Cl. perfringens but significantly inhibited the toxin production. Conclusions:  Lysozyme inhibited the growth of Cl. perfringens type A at 156 μg ml−1. At sublethal levels, lysozyme was able to inhibit the α‐toxin production. Significance and Impact of Study:  Inhibition of Cl. perfringens type A and its α‐toxin production by hen egg white lysozyme had never previously been reported. By inhibiting this avian pathogen and its toxin production, lysozyme showed potential for use in the treatment and prevention of necrotic enteritis and other Cl. perfringens type A related animal diseases.