Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the proposed modification of the terms of the authorisation regarding the maximum inclusion level of a feed additive consisting of nonanoic acid for all pigs and poultry species. Nonanoic acid is currently authorised for use as a sensory additive (functional group: flavouring compounds) for all animal species at a recommended maximum content of 5 mg/kg complete feed. The applicant is requesting a modification of the authorisation to increase the recommended maximum content of the active substance from 5 to 100 mg/kg complete feed for all poultry and pig species. In support of the safety of the additive at the new proposed level, the applicant provided tolerance trials in the target species. The FEEDAP Panel concludes that nonanoic acid is safe for all growing poultry species and Suidae at 100 mg/kg feed. The Panel cannot conclude on the safety of the new proposed level (100 mg/kg complete feed) for laying hens, turkeys for breeding, minor poultry species for laying/breeding and reproductive Suidae. However, FEEDAP Panel considered that nonanoic acid is safe at 10 mg/kg complete feed in laying hens, turkeys for breeding, minor poultry species for laying/breeding and 20 mg/kg complete feed for reproductive Suidae. The use of the feed additive in animal nutrition under the conditions of use proposed is of no concern for the consumer and the environment. Due to the lack of data, the FEEDAP Panel cannot conclude on the potential of the additive to be a skin and eye irritant neither a dermal nor respiratory sensitiser. No further demonstration of efficacy is necessary.