Verbal fluency tasks have been widely used in clinical neuropsychology and they are important indicators for different conditions. The aim of this study was to examine sex difference in written verbal fluency task in a sample of adolescents from different cultures than those studied so far, using stimulus letters specific for the language of that culture. Participants were high-school students (N=233, 40% males), aged between 14 and 19 years (M=16.66, SD=1.26). Participants were asked to produce as many words as they can, longer than three letters, starting with letters K and M. These letters were chosen according to Mimica et al. (2011) study on appropriate phonological verbal fluency stimulus letters for use with Croatian speaking individuals. Scores of females and males obtained for letters K and M were compared using ANOVA. Females performed better with Cohen d 0.68 for letter K and 0.54 for letter M. This sex difference in verbal fluency in adolescence might be related to sex differences in the regional timing of brain maturation or to sex difference in writing speed. Future studies should further test alternative explanations for this sex difference in adolescence, which seems to become smaller or disappear in adulthood.