Two experiments were conducted to examine effects of a commercial phytogenic feed additive (PFA), containing inulin, an essential oil mix (carvacrol, thymol), and chest nut meal (polyphenols) on nutrient digestibility, protein utilization, and lysine efficiency in piglets. Each experiment utilized sixteen piglets (male castrated, 8 wk) and four experimental groups. Experiment 1 studied graded levels of the PFA (0, 0.05, 0.1, 0.15%) in lysine limited diets (wheat, barley, soyabean meal, fish meal). Experiment 2 examined 0.1% of the PFA and two dietary levels of lysine. The results indicated that apparent nutrient digestibility, protein utilization, and lysine efficiency were not significantly affected by the PFA (P>0.05). Observed daily lysine requirements (7.3, 9.9 and 13.1 g for 76, 100, 124 g daily protein deposition) in growing barrows (20-30 kg body weight) were in line with recommendations and contribute to the limited database for modelling of lysine requirements in piglets.