This study investigated the effect of mindfulness-based cognitive therapy (MBCT) on mathematics anxiety among students in Nigerian secondary schools. Eighty-six senior secondary class one students (aged 15-16 years) participated, comprising 43 students allocated to the experimental group and 43 students allocated to the control group. Mathematics anxiety was measured using the Mathematics Anxiety Rating Scale (MARS). The experimental group participated in a MBCT intervention, whereas the control group underwent conventional counselling. Both conditions lasted 6 weeks and included 12 sessions, 90 min each. Results revealed that MBCT reduced students' mathematics anxiety from pre- to post-test, and the effect remained consistent at follow-up, compared to the control group. One of the recommendations was that teachers should be trained in applying MBCT to anxious mathematics students to remove the fear response of mathematics.