The main objective of this review was to highlight the current aspects of the use of EOs as feed additives, in terms of advantages, benefits, as well as some limitations of their applications. The complexity of EO composition and the related diversity of their biological activities is discussed in relation to effects on animal health and animal products performance. Finally, studies of EO delivery techniques as feed additives are stressed, with a focus on encapsulation as a promising approach for the improvement of feed quality and for animal health benefits.