Abstract Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of l‐lysine sulfate produced by the genetically modified strain Escherichia coli CGMCC 7.398 as a nutritional feed additive for all animal species. Neither the production strain nor its recombinant DNA were detected in the final product. The additive does not pose any safety concerns associated with the production strain. The additive under assessment is considered safe for the target species. When using l‐lysine sulfate, the background sulfur/sulfate content in the compound feed should be taken into account. l‐lysine sulfate produced by E. coli CGMCC 7.398 is safe for the consumers and for the environment. In the absence of data, the FEEDAP Panel cannot conclude on the potential of the additive under assessment to be irritant to skin or eyes, or on its potential to be a dermal sensitiser. The endotoxin activity of the additive represents a risk by inhalation for users handling the additive. The additive l‐lysine sulfate is considered as an efficacious source of the essential amino acid l‐lysine for non‐ruminant animal species. For the supplemental l‐lysine to be as efficacious in ruminants as it is in non‐ruminant species, this would require protection against degradation in the rumen.