Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of K‐9 Heritage Probiotic Blend® when used as a zootechnical additive (functional group: gut flora stabilisers) for dogs. The product under assessment is based on viable cells of Lacticaseibacillus casei IDAC 210415‐01, Limosilactobacillus fermentum IDAC 210415‐02, Levilactobacillus brevis IDAC 051120‐02 and Enterococcus faecium IDAC 181218‐03. The FEEDAP Panel was not in the position to conclude on the identification of the strains and, therefore, the safety of the product cannot be based on the presumption of safety of the active agents. The Panel notes that the use of E. faecium IDAC 181218‐03 represents a safety concern because it harbours an acquired antimicrobial resistance gene. Moreover, the hazard related to the presence of additional antimicrobial resistance genes in the active agents cannot be excluded. No tolerance trials on the target animals have been provided. Therefore, the Panel is not in the position to conclude on the safety of the additive for dogs. Regarding the user safety, the Panel cannot conclude on the irritant potential of the additive for skin or eyes due to the absence of data. Given the proteinaceous nature of the active agents, the additive should be considered a respiratory sensitiser. No conclusions could be drawn on its potential to be a skin sensitiser. The use of K‐9 Heritage Probiotic Blend® in animal nutrition represents a safety concern for the environment due to the potential carryover of at least an antimicrobial resistance gene. The FEEDAP Panel is not in the position to conclude on the efficacy of K‐9 Heritage Probiotic Blend® for the target species.