The present study aimed to determine the effect of feeding time on growth and nitrogen excretion in juvenile sole. An 84-day growth trial was conducted, in which food was supplied to three triplicate groups of juvenile Senegalese sole (3 g wet weight) at different schedules – diurnal, nocturnal and mixed. At the end of the growth trial, ammonia and urea excretion was assessed during a 24 h cycle. Improved growth (1.3% vs. 0.9% day−1, specific growth rate), higher nitrogen retention (0.35 vs. 0.27 g N kg−1 day−1), lower ammonia excretion (209 vs. 272 mg N-NH4 kg−1 day−1) and lower total nitrogen excretion (278 vs. 352 mg N kg−1 day−1) were found in daytime-fed fish compared with night-fed fish. Fish in the mixed feeding regime showed intermediate values of ammonia and total nitrogen excretion, but did not differ from day-fed fish regarding the other parameters. Results indicate that juvenile sole at a period of their life cycle appear to use more efficiently dietary protein for somatic growth under a diurnal than under a nocturnal feeding regime. This suggest that at least during a time-window in the juvenile rearing a diurnal feeding regime might be more effective in the production of this species.