Abstract Following a request from the European Commission, the Panel on Additives and Products or substances used in Animal Feed (FEEDAP Panel) was asked to deliver a scientific opinion on the safety and efficacy of the coccidiostat Monimax® (monensin sodium and nicarbazin) when used in feed for turkeys or chickens for fattening. In previous assessments (2017, 2018), the FEEDAP Panel could not conclude on the safety of Monimax® for the environment due to concerns on monensin sodium and 4,4′‐dinitrocarbanilide (DNC, one of the moieties of nicarbazin). The applicant provided additional information that has been assessed. The use of monensin sodium from Monimax® in complete feed for chickens for fattening, chickens reared for laying and turkeys for fattening poses no risk for the aquatic compartment, the terrestrial compartment or for sediment. The bioaccumulation potential of monensin in the environment is low. No concerns would arise for the 4,6‐dimethylpyrimidin‐2‐ol (HDP) moiety of nicarbazin excreted from chickens for fattening, chickens reared for laying and turkeys fed Monimax®. The use of DNC moiety of nicarbazin from Monimax® in complete feed for chickens for fattening, chickens reared for laying and turkeys for fattening poses no risk for the aquatic compartment, the terrestrial compartments or for sediment. The bioaccumulation potential of DNC in the environment is low and the risk for secondary poisoning is not likely to occur