This study systematically evaluates the effects of dietary supplementation with phytogenic feed additive (0.2%, 0.4%, and 0.8%) on white-feathered broilers (n = 88) through a 42-day controlled trial with the weight of approximately 50 g. The experimental design incorporates a triplicate-group-replicated protocol with daily feed intake monitoring, culminating in comprehensive assessments of the growth performance, slaughter traits, meat quality, and cecal microbiome dynamics. The results demonstrated that the 0.8% supplementation significantly enhanced average daily weight gain ( < 0.05), optimized meat characteristics (elevated the redness of meat, reduced pH; < 0.05), and restructured cecal microbiota by enriching and ( < 0.05). Based on microbiota-based functional prediction analyses (COG/KEGG/MetaCyc), phytogenic feed additive significantly activated lipid metabolism pathways in broilers. The immunomodulatory correlations between and immune indicators suggested their potential immune-enhancing effects mediated through host immune regulation. The findings established the 0.8% phytogenic feed additive as a multifunctional phytogenic additive that synchronously improves zootechnical performance, meat quality, and microbiome homeostasis, offering a scientifically validated strategy for antibiotic-free precision nutrition in sustainable poultry production.