The Galápagos sea lion, Zalophus wollebaeki, is an endemic and endangered species subject to population decline associated with environmental variability, such as El Niño events, constant feeding stress, and exposure to diseases through contact with introduced species. Reference blood parameter intervals have been published for some pinniped species, but baseline biochemical and blood gas values are lacking from Z. wollebaeki. We analyzed blood samples from 30 juvenile Galápagos sea lions (19 females, 11 males) captured in two rookeries on San Cristóbal Island. A portable blood analyzer (iSTAT) was used to obtain nearimmediate field results for pH, partial press‐ ure of O2, partial pressure of CO2, bicarbonate (HCO3−), hematocrit (Hct), hemoglobin, Na, K, ionized Ca, and glucose, and blood lactate was measured using a portable Lactate PlusTM analyzer. Average heart rate, biochemistry, and hematology parameters were comparable with healthy indi‐ viduals of other pinniped species. Hemoglobin was significantly correlated with body condition of juv‐ enile Galápagos sea lions. When compared with available blood values of clinically healthy California sea lions, Galápagos sea lions had higher total protein and Hct and lower Ca and K levels. Our results provide baseline data that may be useful in comparisons among populations and in detecting changes in health status among Galápagos sea lions.