The experiment was conducted to evaluate the efficacy of a phytogenic feed additive (PFA) on body weight gain, carcass composition and quality of 72 fattening pigs [(Large White × Landrace) × Piétrain)]. Animals were distributed into 3 treatment groups with 3 replicates of 8 pigs per replicate, with an initial weight of 32.2 ± 0.4 kg. Control group (CON) and one phytogenic group (PFA+normal; Digestarom® Finish 150 ppm, BIOMIN Phytogenics GmbH, Germany) received a diet containing 17% and 15% CP in the growing and finishing period, respectively. Another phytogenic group (PFA+low; Digestarom Finish 150 ppm) received a ration with a reduced protein content (−0.4% CP) throughout the whole growing and fattening period. Feed and water was provided ad libitum. At 73.2 ± 0.6 kg of BW, feed changed from growing to finishing diet. Body weight was measured weekly and individual feed intake was recorded daily. Pigs were slaughtered at 117.5 ± 0.2 kg and carcass composition and quality were evaluated. Data were analyzed with procedure GLM (SAS 9.4) and a multiple comparison was conducted with Tukey’s range test. Results for the whole fattening period show significantly improved gain:feed ratio (P < 0.05; 0.389 and 0.388 in PFA+normal and PFA+low, respectively, compared with 0.368 in CON). Average daily feed intake was 2298 g/d in the CON compared with 2288 g/d in the PFA+normal and 2275 g/d in the PFA+low group. Daily weight gain tended to be higher (0.05 < P < 0.10) in the PFA+normal and PFA+low group (889.0 and 881.7 g/d) compared with CON (844.5 g/d). Carcass composition and quality parameters did not differ significantly (P > 0.05) between treatments besides conductivity of meat which has been improved for PFA+low group compared with CON 1 h post mortem (4.35 vs. 5.02 mS/cm, respectively). Overall, the supplementation of a PFA improved the performance of pigs and a protein reduction was efficiently compensated through the supplementation of PFA.