The objective of this study was to evaluate effects of photoperiod management on behavioral responses in lactating dairy cows. Thirty lactating cows (days in milk = 115 ± 33, body weight = 617 ± 70 kg) were subjected to a long-day photoperiod (LP; 16 h/d light) or a short day photoperiod (SP; 8 h/d light) in a tiestall barn (n = 15 per treatment). Data and samples were collected before animals were assigned to treatments and after a 21-dadaptation period. Feeding behavior data were summarized for 4 time periods based on light management: Period 1 (7 p.m. to 3 a.m.; both treatments had no light), Period 2 (3 a.m. to 8 a.m.; only LP treatment had light), Period 3 (8 a.m. to 4 p.m.; both treatments had light), and Period 4 (4 p.m. to 7 p.m.; only LP treatment had light). All response variables were analyzed using a model including fixed effect of treatment, time, and treatment by time interaction with FIT Model Procedure of JMP. Period by treatment interaction was not observed for DMI, milk yield, lying time, or overall feeding behavior. However, in Period 2 (3 a.m. to 8 a.m.), there was a time by treatment interaction for lying time (P = 0.015); LP treatment decreased lying time by 5.5 min/h while SP treatment did not. There was also tendency of an interaction for eating time (P = 0.064); LP treatment increased eating time by 5.1 min/h while SP treatment did not. In addition, tendency for period by treatment interaction was observed for sorting behavior (P = 0.08). The LP cows sorted, to a less extent compared with SP cows, against long particles (sorting index for particles on the screen with 19-mm pores: 91.4 vs. 78.0), and for small particles (sorting index for particles through the screen with 1.18-mm pores: 101.5 vs. 104.2). These results suggest that the provision of supplementary light may reduce sorting and modulate behavior in dairy cows, and that the behavior response to LP may differ depending on time of day in which supplementary light is given.