One of the aims of this study is to examine whether the worst experiences and most troublesome mathematics classroom experience affect mathematics anxiety in pre-service elementary teachers. Another goal is to find out how the causes of their anxiety relate to these negative experiences. The participants were 167 senior elementary pre-service teachers. Three different instruments were used to collect data; Mathematics Anxiety Rating Scale, Worst Experience and Most Troublesome Mathematics Classroom Experience Reflection Test, and Interview Protocol. The findings show that many pre-service teachers have mathematics anxiety and that the worst experience and the most troublesome mathematics classroom experience have a direct influence on mathematics anxiety in pre-service teachers. Also, the majority of instances of participants' mathematics anxiety are caused by the teachers, their behavior or teaching approaches in their past.