The current study was conducted to investigate the effects of dietary iron-loaded chitooligosacharide nanoparticles (Fe-CNP) on occurrence of bacterial chondronecrosis with osteomyelitis (BCO) in broiler chickens. Four hundred eighty day-old chicks (Ross 308) were assigned to four treatments with six replicates of 20 birds. All chicks were reared on wire flooring system up to 42 days of age. The control diet was formulated to meet the Aviagen recommendations except for iron supplement. The experimental groups were contain: 10 mg/kg Fe from Fe-CNP (group Fe-CNP), 20 mg/kg Fe from FeSO4 (group FeSO4) and 20 mg/kg Fe from FeSO4 + CNP (group FeSO4+CNP). Results showed a significant increase in production efficiency factor, weight gain and FCR in all Fe supplemented groups (P<0.05) compared to the control. Feed intake was not differed significantly between groups (P>0.05). Serum tumor necrosis factor-alpha (TNF-α) level decreased significantly by Fe-CNP, whereas serum immunoglobulin G (IgG) level increased significantly in this group (P<0.05). The prevalence of impaired gait scores (GS≥3) in live birds in day 42 did not show a significant difference between dietary treatments (P>0.05). Lame broilers evaluation showed that lower control and Fe-CNP had lower impaired gaits (P<0.05). Supplementation of FeSO4 significantly increased the percentage of femur and tibia lesions (P<0.05). Leg evaluation of live broilers showed that Fe-CNP and control groups exhibited a higher incidence of normal femur (NF) and a lower percentage of transitional femur necrosis (FHT) and total femur lesions (All F; P<0.05). Femoral head necrosis (FHN) and FHS were not affected significantly by dietary treatments (P>0.05). Totally, Fe-CNP supplement, by improving immune system, reduced the prevalence of BCO lesions in broiler chickens. تفاصيل المقالة