AbstractSize of canine teeth from California sea lion (Zalophus californianus californianus) carcasses is shown to be useful in determining the sex of animals which have missing genitalia or which are otherwise of unknown sex. A total of 267 canine teeth from carcasses of 68 males and 43 females were measured along five axes. Of root and crown measurements of upper and lower canines, males and females overlapped only in root thickness of upper canines. A multivariate ANOVA showed a significant difference in the size of canines between upper and lower canines, and between males and females. Stepwise discriminant analysis produced discriminant functions for upper and lower canines for determining sex of unknown‐sexed California sea lions. A separate set of canine teeth from 39 male and 49 female California sea lions was correctly classified without prior knowledge of sex by visual inspection and by the two discriminant function