The study investigate the effect of feeding low available phosphorus (AP) diet supplemented with three levels of microbial phytase (MP) and /or three levels of citric acid (CA) on broiler performance, tibia bone and nutrient retention. Four hundred day- old Ross broiler chicks were randomly allocated into ten treated groups, with four replicates of 10 birds each. The chicks were fed ten different diets as normal phosphorus 0.45% AP (positive control, PC) and nine groups with phosphorus deficient diets 0.25% AP (negative control, NC) supplemented with three CA levels as 0%, 1% or 2% and / or MP levels 0, 500 and 1000 FTU/Kg. The results indicated that supplementation of MP and /or CA into NC diet significantly improved body gain of chicks. Feed intake significantly increased due to adding 1% CA and MP levels into NC diet. Feed conversion ratio improved due to supplementing MP or CA into NC diet. There is no significant effect on tibia width and breaking strength by adding MP and/or CA into NC diet. Adding MP into NC diet significantly improved tibia length, weight, and ash content while, citric acid affected significantly at the first stage of growth only. Blood phosphorus increased significantly by supplementing MP into NC diet at the 5^th week of age, while blood calcium was not affected significantly by MP and/or CA. Tibia calcium of chicks fed NC diet was higher than those fed PC diet or NC diet enriched with MP and/or CA. Tibia phosphorus did not response clearly for adding MP or CA into NC diet. Nitrogen and calcium retention of chicks fed NC were significantly lower than those fed PC or NC diet supplemented with 1000 FTU/kg MP and CA. Phosphorus retention of chicks fed NC diet was significantly similar for those fed PC or NC diets supplemented with MP and/or CA. It can be concluded that adding MP at 500 FTU/kg level with 1% CA into NC diet was effectiveness to improve body weight gain and tibia bone characteristics as like as those fed PC or NC diet enriched with 1000 FTU/kg MP.