Herbal feed additives (HFAs) have emerged as promising alternatives to antibiotics in poultry nutrition, particularly following the ban on antibiotic growth promoters (AGPs) and the growing interest in antibiotic-free production. The aim of this review was to discuss the potential effects of various HFAs on improving growth performance, enhancing antioxidant defenses, modifying intestinal microflora and morphology, modulating immune responses, and regulating genetic and hormonal functions in poultry. HFAs have notable antioxidant and immunomodulatory properties that help reduce oxidative stress and boost immune responses, thereby enhancing overall health and productivity. Furthermore, HFAs provide antimicrobial and intestinal health benefits by promoting gut eubiosis, fostering growth of beneficial microbiota, and offering protection against pathogens. Additionally, certain HFAs can affect genetic and hormonal regulation, which play a vital role in enhancing immune function and improving both reproductive and overall performance. These effects are particularly valuable for sustainable poultry production and reducing reliance on AGPs is becoming increasingly important. While the benefits of HFAs are well documented, further research is necessary to determine their optimal levels, potential interactions with other dietary components, and long-term effects on poultry health and productivity. This review highlighted the importance of herbs and their derivatives in poultry diets to support sustainable and efficient poultry production.