Behavioral studies in non-human primates have become ideal models for further investigations into advanced cognitive function in humans. To date, there is no systematic ethogram of the cynomolgus monkey (Macaca fascicularis) in a free enclosure. In a field observation of 6012 subjects, 107 distinct behaviors of M. fascicularis were preliminarily described. 83 of these behaviors were then independently validated through a randomized cohort and classified into 12 behavioral categories. 53 of these behaviors were then selected to accurately reflect the daily mundane activity of the species in a free enclosure. These findings systematically document the behavior of M. fascicularis in a free enclosure for use in further investigations.