Abstract Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the assessment of the application for the renewal of the authorisation of dicopper chloride trihydroxide as a nutritional feed additive. The additive is currently authorised for use in all animal species (3b409). The applicant is requesting a modification in the current authorising specification: (i) replacing the alpha crystal form paratacamite with clinoatacamite; (ii) removing the ratio between crystal polymorphs from the authorising specification; (iii) changing the minimum for particles below 50 μm from 1% to 5%. The FEEDAP Panel considers that the proposed modifications do not introduce concern for the safety for the target species and that the additive remains safe for the target species and the consumers when used up to the maximum authorised levels. Regarding the safety for the environment, the use of the additive in feed for terrestrial animals and land‐based aquaculture is considered safe under the proposed conditions of use. The data available do not allow the FEEDAP Panel to reach a conclusion on the safety of the additive for marine sediment when it is used in sea cages. The additive is not corrosive to skin, but is an eye and skin irritant. Due to the nickel presence, it is considered a skin and respiratory sensitiser. There is no need for assessing the efficacy of the additive in the context of the renewal of the authorisation.