This experiment aimed to evaluate the effects of in ovo injection of 25-hydroxycholecalciferol (25-OH-D3) and Vitamin K-3 on growth performance, bone calcification and immune system responses in male Ross 308 broilers. Twelve treatment groups with a total number of 768 experimental hatching eggs, four replications and 16 eggs in each replication were selected to form a completely randomized design of factorial arrangement. Treatments included: (1) distilled water, (2) 0.4 mu g D-3, (3) 0.4 mu g D-3 + 2 mu g K-3, (4) 0.4 mu g D-3+ 6 mu g K-3, (5) 0.6 mu g D-3, (6) 0.6 mu g D-3 + 2 mu g K-3, (7) 0.6 mu g D-3 + 6 mu g K-3, (8) 0.8 mu g D-3, (9) 0.8 mu g D-3 + 2 mu g K-3, (10) 0.8 mu g D-3 + 6 mu g K-3, (11) 2 mu g K-3 and (12) 6 mu g K-3. Eggs were transferred to corresponding hatching baskets on the 18th day of incubation and received 0.5 ml of experimental solutions specific to each treatment. The results of our experiments showed that Treatment No. 4 ranked the best out of those administered; holding the highest level of weight gain, feed intake during the breeding period (grower and finisher), bone calcium and phosphorus concentration, and tibia fractural force, (p < 0.05). Treatment No. 4 also showed a significant increase in antibody titer against the SRBC. Maximum stimulation to PHA injection also belonged to this treatment. In contrast, treatment No. 1 held the greatest alkaline phosphates amount (p < 0.05). No improvements were observed in calcium egg shells compared to the control group. Our data implies that appropriate levels of Vitamins D-3 and K-3 in ovo injection has beneficial effects on growth performance, immune system and bone development. (C) 2017 Elsevier Inc. All rights reserved.