The green sea turtle (also known locally as black turtle; Chelonia mydas) is 1 of 5 species of sea turtles found along the coast of the state of Baja California Sur, Mexico, where several bays and lagoon systems provide an important growth and feeding habitat. We characterized blood biochemistry values of 67 green turtles captured at 2 mangrove estuaries along the Pacific coast of the Baja California Peninsula, Mexico, from 2005 to 2007. Blood samples were collected from live turtles for biochemical analysis of 18 parameters and analyzed by physical state (healthy, injured), size classes, season, and geographic location. Green turtles showed differences in the variability of the biochemical parameters between the 2 sites. In Punta Abreojos, injured sea turtles had lower calcium (28%), potassium (28%), and inorganic phosphorus (34.5%) levels and higher cholinesterase activity (16%) compared to healthy turtles. Juvenile turtles collected in Bahía Magdalena had higher glucose levels (34%) than subadults. Levels of triglycerides, total proteins, and albumin correlated positively with size. During the summer and during the years 2005 (Bahía Magdalena, BMA) and 2006 (Punta Abreojos, PAO), individuals had significantly higher concentrations of lipid (cholesterol and triglycerides), glucose, uric acid, and protein. Differences in the habitat, food availability, and environmental conditions between BMA and PAO were reflected in the variability of the biochemical parameters when compared by different factors, such as physical state, size, and seasonality. This is the first report of blood biochemical values of green sea turtles in the Pacific coast of Baja California, Mexico. All serum chemistry values of green sea turtles were within published reference ranges of healthy sea turtle population.