This experiment was conducted to evaluate the effects of different Zn sources and microbial phytase supplemented to low available P (aP) corn-soy diets on morphometric indices of tibiotarsi, bone strength and Zn accumulation. The experimental period lasted 42 days. A total of 875 one-day-old Ross 308 male broiler chicks were randomly assigned to seven treatment groups (positive, negative and five experimental), each with five identical subgroups of 25 birds. The positive control (PC) group was fed a diet containing adequate concentration (0.45%) of available phosphorus (aP) due to mineral premix (except zinc) and feeds; the negative control (NC) group was fed a basal diet including low concentration (0.30%) of available phosphorus (aP) due to mineral premix (except zinc) and feeds; 0.30% aP and 500 FTU phytase kg-1; 0.30% aP and 75 mg Zn-proteinate kg-1; 0.30% aP and 75 mg ZnSO4 kg-1; 75 mg Zn-proteinate and 500 FTU phytase kg-1; 75 mg ZnSO4 and 500 FTU phytase kg-1 were added to the experimental groups of phytase (PH), organic zinc (OZ), inorganic zinc (IZ), organic zinc + phytase (OZ+PH) and inorganic zinc + phytase (IZ+PH) respectively. There were no significant differences among the groups in mean tibiotarsal diaphysis diameter, thickness of the medial wall, tibiotarsal index, medullary canal diameter, modulus of elasticity or breaking stress. However, diet with OZ + PH and IZ + PH supplementation had a greater influence on tibiotarsal weight and tibiotarsal weight/length index when compared to those measurements in broilers in both control groups (P<0.001). In addition, feed additives were seen to have a significant effect on tibiotarsal length (P<0.01), robusticity index (P<0.001), thickness of the lateral wall (P<0.05) and Zn content (P<0.05). In conclusion, the study indicated that the use of organic and inorganic Zn alone or in combination with microbial phytase improved tibial bone traits and Zn content.