The aim of the study was to try to find a quick and cost-effective way of predicting the gender of adult Chilean flamingos Phoenicopterus chilensis using biometric measurements alone. Three biometric measurements (tarsus length, flat wing length and body mass) were taken from a group of 68 [38.30 (♂.♀)] Chilean flamingos of known sex at Dublin Zoo. The measurements were compared to see which if any of them were useful in predicting the gender of individual birds. Only maximum tarsus length provided a useful measurement in predicting gender. Maximum tarsus measurement alone was enough to predict the sex of over 94% of adult birds. All adult birds with a tarsus length of ≥26·0 cm were ♂. All adult birds with a tarsus length of ≤25·5 cm were ♀.