Circadian rhythms in the behavior and physiological processes are commonly observed in the living organisms including teleosts. The objective of this study is to investigate the circadian rhythmic changes of the hematological parameters such as hematocrit (Hct), hemoglobin (Hb), and the physiological parameters such as plasma glucose and lactate in 3 to 4 years old black porgy (Acanthopagrus schlegeli) of both sexes under ambient conditions. The results showed that only the Hb showed significant circadian rhythm, on the other hand, Hct, glucose and lactate did not show obvious circadian rhythms. In addition, the Hb, glucose and lactate showed significantly sexual difference (P < 0.05). All of the values in male fish were higher than those in female ones at each time point. Hct also had a similar phenomenon but the difference between the both sexes did not reach the significant level (P > 0.05).