The Pacific mackerel Scomber japonicus aquaculture is receiving growing attention, and further development of this industry is expected to protect wild stocks. Information on S. japonicus hematology is very limited. Therefore, the present study aimed to provide the hematological and serum chemistry profiles associated with sex and some seasonal variations in Pacific mackerel from Todos Santos Bay, Baja California, Mexico. Fish were sampled in April (spring) and August (summer). Results showed that the condition factor and all blood parameters analyzed in male and female mackerel were not affected by sex (P > 0.05). The seasonality effect on the mackerel was observed in some blood parameters such as mean corpuscular hemoglobin, total protein, globulin, and triglycerides that exhibited lower values in April compared to August (P < 0.05). While white blood cell count was higher in August (P < 0.05) compared with April. The fish sampled during the two sampling times were possibly a heterogeneous group of ages (1 to 3 years) with lengths ranging from 20 to 30 cm. Consequently, there is an urgent need to follow doing reference interval databases to assess Pacific mackerel health status under different conditions.