Counterstory, an analytical tool of Critical Race Theory, was used in this dissertation to foreground the voices of four young Black men completing a non-credit bearing developmental or remedial mathematics (DevRemMath) course at Suburban Community College (SCC). This study presents young Black men's first-person perspectives about the conditions that determined their learning and doing of postsecondary mathematics, which is operationalized in this dissertation as "participation." Their narratives further clarify the race-gender dimensions of participation, and the factors that promoted or deterred participation in DevRemMath at SCC. The study offers several implications for advancing racial justice in DevRemMath and postsecondary mathematics learning, which include reframing how faculty and administration respond to the needs of young Black men in planning and delivering DevRemMath instruction, as well as naming the significance of faculty interactions with young Black men to counter barriers to their academic success. The dissertation concludes with recommendations for (re)structuring DevRemMath spaces in order to better strengthen young Black men's participation in the learning and doing of postsecondary mathematics. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]