This sequential exploratory mixed methods study addressed the problem of low academic achievement in mathematics, specifically for African American middle school students who historically score below proficient levels on standardized mathematics assessments. The purpose was to investigate the effectiveness of the Project-Based Learning (PBL) approach on African American students' academic achievement, and to determine what factors, if any, impact African American students' motivation during PBL mathematics. Eight sixth-grade students from a private school in the southeastern United States, identified as performing below proficient level in mathematics, participated in this study. Data collection included two focus group interviews, a sixweek PBL mathematics unit, classroom observations, and a pre-and post-benchmark assessment. The quantitative results indicated that on average, the students performing below proficient level significantly improved their performance from the pre-test to the posttest. However, their scores were significantly lower than the students who historically performed at math proficient levels, and the PBL unit did little to close the achievement gap. The qualitative data suggest three factors, student perceived level of rigor of the mathematics assignments, the nature of the peer-to-peer interactions, and the presence of classroom-based student activities that the students perceived to be fun and valuable, impact the students' motivation in PBL. Recommendations for future research include studies of long term impacts on mathematics academic achievement and motivation when students are immersed in PBL over longer periods of time and studies comparing students' mathematics scores on the SAT or ACT that completed PBL instruction opposed to more traditional methods. [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.]