Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of essential oils from fruit and stems of Foeniculum vulgare Mill. (bitter fennel oil and sweet fennel oil), when used as sensory additives (flavourings). For long‐living and reproductive animals, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) considered of low concern the use of bitter fennel oil (with a content of estragole up to 6.1%) at the proposed use level in complete feed: 0.6 mg/kg for laying hens and rabbits, 1.0 mg/kg for sows and dairy cows, 1.5 mg/kg for sheep/goats, horses and cats, 1.9 mg/kg for dogs and 7.1 mg/kg for ornamental fish. For short‐living animals (animals for fattening), the Panel had no safety concern when bitter fennel oil is used at the proposed use level in complete feed of 18.2 mg/kg for chickens for fattening, 24.3 mg/kg for turkeys for fattening and 25 mg/kg for piglets, pigs for fattening, veal calves, cattle for fattening, sheep/goats, horses, rabbits and salmon. These conclusions were extrapolated to other physiologically related species. The use of sweet fennel oil (with a content of estragole up to 5.0%) was considered of low concern at the proposed use level in complete feed of 2.3 mg/kg for dogs and 1.9 mg/kg cats. The use of bitter fennel oil in animal feed is expected to be of no concern for consumers and the environment. The additives under assessment should be considered as irritants to skin and eyes, and as dermal and respiratory sensitisers. Due to the high concentration of estragole (> 1%), fennel oils are classified as suspected of causing genetic defects and of causing cancer and should be handled accordingly. Since the fruit of F. vulgare Mill. ssp. vulgare and its preparations are recognised to flavour food, no further demonstration of efficacy was necessary.