In order to increase mathematics achievement, persistence, and participation in mathematics-related careers and majors for African American adolescents, researchers have discussed the need for students to develop positive mathematical identities (English-Clarke, Slaughter-Defoe, & Martin, 2012; Gutstein, 2003; Larnell, 2013; Martin, 2000, 2006, 2007, 2009). These studies and others have implied that the classroom teacher plays a critical role in either bolstering or limiting the formation of a positive mathematics identity of the students in their classes. However, there still remains a lack of clear understanding of how mathematics identity manifests and operates in African American students. In addition, research has yet to yield lucid descriptions of the characteristics of an effective mathematics teacher for African American adolescents that supports positive mathematics identity development. This mixed-method study examines the relationship between developing racial and mathematical identities of 102 African American adolescent students in mathematics across five public secondary schools. Quantitative research centred on student surveys that probed on various dimensions of their mathematical proclivities and their racial-mathematical beliefs. This study also included a qualitative investigation into the characteristics of two designated "effective" teachers from two adjacent school districts in the rural, southeastern U.S. Findings indicate a positive association between students' racial identity and their overall mathematics identity and provide support of mathematics identity theory in contemporary research (Martin, 2000). In addition, findings showed descriptions of teachers designated as "effective" by their beliefs, demeanors, and practices engaging African American adolescents. The results unearth the resilience of problematic perspectives and practices among the sample of teachers that could impede further progress of African American adolescents in mathematics. The study critically examines the implications regarding what it means to be an "effective" mathematics teacher of African American adolescents. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]