This study reports body mass and serum chemistry reference values of 121 male and 57 female Nazca boobies (Sulidae: Sula granti) from a colony on Isla Española, Galápagos Islands, Ecuador. Circulating aspartate aminotransferase, creatine kinase, lactate dehydrogenase, total protein, immunoglobulin Y, uric acid, blood urea nitrogen, triglycerides, cholesterol, and creatinine were quantified and analyzed by sex. Sex explained little variance in all examined variables except mass; females were heavier than males, as expected for sulids. Uric acid values had a bimodal distribution, likely reflecting differences in recent foraging success. Aspartate aminotransferase and creatine kinase values were similar to those reported in other sulids. Clinical health reference values are critical for practitioners investigating responses of seabirds to oil spills, coastal restoration efforts, or emerging diseases. These data from a species living in a relatively isolated and pristine area provide a valuable baseline for future health evaluations.