This study investigated the effects of in-ovo injection of manganese on some organ weights and length in quail hatching (Coturnix coturnix japonica) eggs.In total, 400 quail hatching eggs were randomly divided into four treatment groups of 100 eggs per treatment with four replicates of 25 eggs each. On the 14th day of incubation, eggs from group 1 were not injected (control(C)), group 2 was injected with Mn-bioplex at 20 µg per egg (Mn20), group 3 was injected with Mn-bioplex at 40 µg per egg (Mn40), and group 4 was injected with Mn-bioplex at 80 µg per egg (Mn80). There were no significant differences among treatments for chick weight, yolk sac weight, liver weight, and heart weight. The highest chick length was obtained from the C treatment. No significant differences were found in chick length among Mn treatment groups. The beak length of C treatment were lower compares with that of the Mn80 treatment group (P<0.05). But no significant differences were observed in beak length among Mn treatments groups. The leg length in C group was significantly lower than Mn40 and Mn80 treatments groups, except Mn20 treatment group (P<0.01). As a result, it can be said that injection of Mn into the hatching quail eggs causes the chick and leg lengths to decrease, and beak length to increase without affecting the weight parameters examined.