Effects of phytic acid (PA) on ileal mineral and amino acid (AA) digestibilities and ileal endogenous AA flow in piglets were investigated. Seven ileal-cannulated weanling pigs were fed a casein–maize starch-based diet with PA (as sodium phytate) at 0, 5, 10 or 20 g/kg in 4 × 4 Latin square design with three added columns to give seven observations per treatment. The basal diet was formulated to meet National Research Council energy and AA requirements for piglets. The respective digestibility and endogenous lysine loss were determined by indicator and homoarginine methods. The apparent ileal digestibility (AID) of Na, K and P was linearly and quadratically reduced (P < 0·05) by increased dietary PA concentration, whereas that of Ca and Mg was only linearly reduced (P < 0·05) by the dietary PA. The AID values for Mg and Na were negative ( − 0·03 and − 0·18, respectively) when PA was supplemented at 20 g/kg. The AID of isoleucine, leucine and valine responded quadratically to dietary PA concentration, though the differences between the AID values of the AA due to change in dietary PA concentration were marginal (at most by 1·8 percentage units). Furthermore, dietary PA did not affect (P>0·05) endogenous AA losses. The results suggest that PA has limited effect on the digestibility and endogenous losses of AA in piglets, but can reduce AID of Mg and Na partly by increasing endogenous losses of these minerals as evidenced by their negative AID values.