Population growth and income increase have promoted a greater consumption of animal-based food. To increase the yield of livestock animals, antibiotic growth promoters (AGPs) have been provided at sub-therapeutic doses in water and feed for production animals. Unfortunately, the misuse of antibiotics has been associated with antimicrobial resistance (AMR), resulting in their ban as animal growth promoters in different countries. In recent years, phytocompounds have emerged as an alternative to substitute the use of antibiotics on livestock. In this context, capsaicinoids and capsinoids from chilli peppers have been evaluated in vitro and in vivo, exhibiting interesting biological activities, such as analgesic, antimicrobial, antioxidant, hypotensive, anticancer, antidiabetic, and slimming effects. Capsinoids and capsaicinoids of chilli pepper have been mostly studied as alternatives to the treatment of obesity; thus, there are several gaps regarding how these phytocompounds enhance weight gain when used as feed additives in animal nutrition and there is no summary of the plethora of research that has been carried out using in extract or powder, in the diet of different species of farm animals that includes the biological effects, suggested doses, and possible mixtures with other phytocompounds or medicinal plants. Therefore, this review addresses updates on the mechanisms of action of AGPs and capsaicinoids from chilli pepper to improve animal health and promote growth and productivity. Additionally, the biological effects on farm animals after the addition of in the diet are summarized, as well as the effective doses to promote growth in chickens, pigs, and ruminants. Finally, future trends and challenges about the use of AGPs and chilli pepper compounds in livestock nutrition are highlighted.