An experiment was conducted to investigate the effects of sodium gluconate and microbial phytase (MP) (Natuphos 1000G) supplementation of diets on performance, mineral retention and bone mineralisation in male broiler chicks from a day old to 21 days of age. The experiment was carried out using a completely randomised design with a 3 by 2 factorial arrangement (0, 2 and 4% sodium gluconate and 0 and 750 U MP/kg diet). Diets were formulated with deficient contents of available phosphorus (aP) (2.4 g/kg). Ten replicate cages of four chicks per replicate cage were fed experimental diets. MP supplementation of diets with deficient contents of aP significantly improved weight gain (P < 0.05) and feed efficiency (P < 0.01). The performance results were similar in birds fed the diets without sodium gluconate and the diets with 2% sodium gluconate. However, the dietary inclusion of sodium gluconate at 4% depressed (P < 0.05) the growth of broiler chickens compared with the diet without sodium gluconate. Compared with the diets supplemented with 2% sodium gluconate, the diets supplemented with 4% sodium gluconate decreased (P < 0.05) weight gain and increased (P < 0.05) feed efficiency. MP supplementation increased (P < 0.01) Ca, P, Mg, Zn retention, and tibia ash, Ca and P contents in tibia ash. Diets with sodium gluconate increased (P < 0.05) P and Zn retention. Diets containing sodium gluconate without phytase increased (P < 0.05) Mg retention and P content in tibia ash. The diet with 2% sodium gluconate without phytase also increased (P < 0.05) Ca retention. The dietary inclusion of sodium gluconate at 2% improved (P < 0.05) tibia ash and Ca content in tibia ash. Sodium gluconate and MP had significant interactions in Ca and Mg retention (P < 0.01), and P content (P < 0.05) in tibia ash. In conclusion, the results indicated that phytase and sodium gluconate supplementation of corn-soybean meal low AP diets increased Ca, P, Mg and Zn mineral retention and bone mineralisation in chicks. The addition of MP improved the performance. However, the supplementation of diets with 4% sodium gluconate depressed the performance.