The search for antibiotic-sparing and climate-resilient strategies has accelerated interest in medicinal plants and phytogenic feed additives in poultry. Reproductive productivity, however, is often inferred from general performance, although the decisive endpoints are egg output, persistency of lay, semen quality, fertility, hatchability, embryo survival, and offspring quality. This structured narrative review integrates evidence from laying hens, breeder hens, and roosters, focusing on the hypothalamic-pituitary-gonadal axis, oxidative stress, gut-liver-reproductive crosstalk, inflammation, and microbial ecology. Meta-analytic evidence suggests that phytogenic extracts can improve egg production and egg mass at moderate inclusion rates, but responses are non-linear and high doses may depress intake or laying performance. Direct male studies indicate that ginger, chive bulb extract, gallic acid, camphor, ginseng-derived compounds, and multi-herb blends can improve semen characteristics, antioxidant status, or reproductive hormones, particularly during aging or heat stress. In breeder hens, phytogenic antioxidant mixtures can support egg traits, oviductal sperm survival, redox balance, and chick quality under thermal challenge. Evidence remains limited by poorly characterized plant materials, inconsistent extraction methods, weak dose-response designs, and under-reporting of fertility and hatchability. Fermented Allium research illustrates a promising translational platform linking phytochemistry, microbial processing, disease resilience, and formulation stability. The field now needs chemically standardized products tested against defined reproductive constraints with fertility, hatchability, safety, and economic endpoints.