Brain-derived neurotrophic factor (BDNF) has been reported to exist not only in nervous tissue but also in serum. In contrast to the wealth of knowledge regarding the various physiological functions of BDNF in the nervous system, information about possible roles in other systems is limited. To elucidate the physiological function of serum BDNF in primates, it is first necessary to establish a method to determine the levels of BDNF in serum of primates. In the present study, we established an enzyme-linked immunosorbent assay (ELISA) method which we used to measure levels of serum BDNF in non-human primates. We found that serum BDNF levels were similar among several species of primates. The present results suggest that our BDNF ELISA may be useful in measuring serum BDNF concentration as a physiological marker, and that levels of serum BDNF may be similar among primates including humans.