Current research has found evidence of effective interventions for mathematics anxiety, both motivational and cognitive interventions can affect learning through instructional design and increased student engagement. Thus, this study investigated whether a combined (cognitive and motivation) intervention approach was more effective than only using a cognitive intervention approach for alleviating mathematics anxiety in middle-school students in order to develop a positive mathematical self-concept. The design used in this study was a comparison pretest-posttest study using the modified Abbreviated Math Anxiety Scale (mAMAS) to measure the participants' level of mathematics anxiety and the STAR Mathematics diagnostic assessment to measure gradual mathematics achievement. Approximately 68 students participated in the combined treatment, and 52 students participated in the cognitive treatment. Both the treatment and comparison groups participated in a 9-week intervention. The cognitive intervention used in this study was incorrect worked examples taught by the comparison group and the treatment group. In addition, a motivation intervention was integrated along with incorrect work examples with lessons to support the development of mathematical mindsets. After the cognitive and combined interventions, the scores for the comparison group on the mathematics anxiety survey showed almost no change whereas the treatment group's score decreased slightly. The difference in posttest means for the two groups was not statistically significant with an effect size close to zero, indicating no difference in posttest means between the two groups. On mathematics achievement, the scores for both groups showed a slight increase. The gain in scores from the pretest to the posttest was not found to be statistically significant. Nonetheless, both groups increased their mathematics grade level from fifth-grade to sixth-grade by the end of the 9-week intervention. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]