Mathematics anxiety is a global phenomenon that has generated research interest over the past four decades. Many researchers have suggested that girls display higher levels of mathematics anxiety than boys. This article explores that conjecture in the New Zealand context. It reports on the prevalence of mathematics anxiety in adolescents and investigates the factors that influence students' mathematics anxiety in mathematics classrooms. Participants in the study were Year 9 students (N = 415) from seven secondary schools in New Zealand. Students were asked to indicate their levels of mathematics test anxiety and mathematics learning anxiety. Statistical analyses confirmed that girls report higher levels of mathematics anxiety than boys. Findings revealed that girls' mathematics anxiety increased with school decile, and was higher in single-sex girls-only schools. Mathematics test anxiety was a major contributor to levels of mathematics anxiety. The article offers a number of strategies that schools might put in place aimed at reducing mathematics anxiety.