We studied the effect of lighting during 19 days of incubation on embryonic bone characteristics, gene ex-pression, thyroid hormones, and glucose in Cobb broiler hatchlings. Eggs (2160) were incubated under darkness (control) and green and white lighting (16D:8L and 12D:12L). On 19th day, tibiotarsal length in-creased under eight hours of white light, and femoral ossified length was longer under eight hours of white and green light. In femur, expression of Alp, Col10a1, and Spp1 increased by 12 h white and 8 h green lighting, and Bglap expression decreased under white. In tibiotarsus, expression of Alp decreased by 8 h lighting (green or white) while Bglap increased by 12 h lighting (green or white). Tibiotarsal expression of Col10a1 increased by 12 h lighting (white and green), and in 8 h green lighting, and Spp1 expression was higher under light illumination. The hatchling blood triiodothyronine concentration in 8 h green lighting was higher than that in control, whereas, thyroxine concentration was lower under 12 h white lighting com-pared with other treatments. Femoral organic matter to mineral (OM:M) ratio and calcium concentration were higher in the eight-hour white light group than in the control, but tibiotarsal OM:M ratio and calcium and phosphorus concentrations were higher under 12 h white light. The findings indicated that lighting dur-ing incubation may impact, both positively and negatively, bone morphology and gene expression. More studies are needed to find the most beneficial lighting system during incubation in chickens. Manuscript profile