Two hundred sixteen early-weaned piglets (initial BW 5.8 ± 1.1 kg) were used to evaluate the effects of microbial phytase (Natuphos®) on growth performance and the digestibility of phosphorus (P), crude protein (CP) and organic matter (OM) in maize-soyabean meal based diets. Pigs were allotted to three treatments with eight pigs per pen and nine pens per treatment. Pigs were phase-fed in two, two-week periods each. Three dietary total P levels combination (DM basis) for pigs in phase 1 and 2 were: 1. control, 0.8 and 6.9 g P/kg diet (1.2 g P/kg diet from dicalcium phosphate - DCP) without phytase, 2. 50% DCP reduction of the control + phytase (50% DCP reduction + phytase), 7.5 and 6.3 g P/kg diet (0.6 g P/kg diet from DCP) and 3. without supplementation + phytase (no DCP + phytase), 6.9 and 5.8 g P/kg diet, respectively. Phytase was added to the phytase-supplemented diets at a level of 500 phytase units/kg of feed for both phases. Chromic oxide (2.5 g/kg) was added to the diets as an indigestible marker to determine coefficient of total tract apparent digestibility (CTTAD) of feed. There were no differences (P>0.05) in overall average daily gain (295, 311 and 297 g/d) and feed/gain ratio (1.47, 1.46 and 1.46) for the control, 50% DCP reduction + phytase and no DCP + phytase diets, respectively. The CTTAD of organic P in the diets with added phytase was significantly higher (P<0.01) than in the control diet in both phase 1 (0.43 and 0.40 vs 0.32) and 2 (0.42 and 0.36 vs 0.28). The CTTAD of organic matter (OM) was also improved by phytase in phase 2. However, the CTTAD of inorganic P and CP was not influenced by phytase supplementation. Serum inorganic phosphorus concentration (119 mg/L) in pigs fed the diet with 50% DCP reduction + phytase was higher (P<0.05) than in pigs fed the control diet (101 mg/L) and the diet without DCP supplementation + phytase (105 mg/L) in phase 2 and was higher on d 1 after weaning than in phase 1 and 2. In summary, phytase supplementation of reduced inorganic phosphorus diets, fed to young pigs, maintained performance and improved the digestibility of organic P and decreased the excretion of faecal phosphorus.