For decades, developmental research has involved the study of sex differences in language acquisition. Many studies of these differences have found a slight advantage in competence for females early in life that seems to wane with age. However, because most of these studies have focused on sex differences in mean values, they have mostly neglected sex differences in variance with males being more variable. In the current study, we examined sex differences in language competence in terms of mean values and variance in large samples (N > 10,000) of German children aged 3–6 years. We administered several tests to assess the children's vocabulary, grammar, speech comprehension, pronunciation, and the processing of sentences and nonce words. Girls performed better than boys in all domains, most often to a statistically significant degree, although the effect sizes were small. Differences decreased with age. Boys varied significantly more than girls in their language competence. In response, we discuss explanations for these findings, as well as recommend directions for future research.