Short wavelength light (blue light) promotes feelings hunger in human, but the effect in calves is unclear. This study aimed to investigate the effect of blue light from white LED on melatonin and appetite-related hormone secretion. Six Holstein heifer calves with a mean body weight of 86.3 kg at 8-wk of age were used and housed in an insulated daylight shed at 20°C with a 16:8 h light-dark cycle (LDPP). Calves were fed a calf starter and kleingrass hay ad libitum. Feed intake was recorded daily and calves were weighed weekly. Animals were assigned to 2 treatments for 3 weeks each in 2 × 2 crossover design as follows: exposed to white LED including blue light (12 µmol/cm²/s, 880 lx) during the light period and no light (0 lx) during the dark period (WHITE), or exposed to 594 nm (yellow) monochromatic LED light (12 µmol/cm²/s, 930 lx) for 2 h before the dark period (YELLOW). Blood samples were collected from a jugular vein on the final day of each treatment. Data were analyzed by ANOVA to determine effects of treatment, time as repeated measures, and their interaction. Dry matter intake (DMI) of calf starter did not differ between the groups, but DMI of kleingrass hay was higher (P < 0.05) in the YELLOW group (236 ± 63.8 g/day; LSM ± SE) than in the WHITE group (152 ± 63.8 g/day). Body weight gain did not differ between the groups. Plasma melatonin concentrations gradually increased from 2 h before the dark period in the YELLOW group (9.11 ± 2.18 pg/mL), but did not increase in the WHITE group (1.78 ± 2.18 pg/mL). Higher plasma melatonin levels were maintained (P < 0.01) during the dark period (21.3 ± 1.81 pg/mL) compared with those during the light period (1.23 ± 1.81 pg/mL) and were not different between the groups. Plasma ghrelin concentrations were higher (P < 0.01) during the dark period than during the light period, and were higher (P < 0.01) for the WHITE group (0.08 ± 0.02 ng/mL) than for the YELLOW group (0.06 ± 0.02 ng/mL). Plasma GLP-1 concentrations were not affected by treatment. Results suggest that exposure to white LED for 2 h before the dark period under LDPP suppresses melatonin secretion and DMI in calves.