Despite more historically underrepresented students pursuing STEM degrees, their likelihood of remaining in STEM fields has been stalled compared with their White peers. It has been argued that developing inclusive programming and environment can significantly impact the retention and persistence of underrepresented undergraduate STEM students in STEM courses. According to the literature, students' self-conceptualization and development of their disciplinary identities are connected to their interest, perseverance, and success in STEM post-secondary environments. However, there is a paucity of scholarship on using critical educational techniques that combine marginalized students' STEM cultural knowledge and applicability. Thus, this qualitative action research study examined the effects of a decolonized STEM curriculum on marginalized students' intersectional identities, perspectives, and experiences in a STEM learning environment at a Midwestern university. This study investigated culturally based instruction that promotes the knowledge of marginalized students neglected in academic settings, which may serve as a resource for STEM educators. I utilized a critical-asset lens to highlight academic and psychological factors that challenge our understanding of race and culture's influence on underrepresented students' attitudes, perceptions, and science identity development while teaching from decolonized STEM curriculum. Thirteen first-year underrepresented STEM students took part in a decolonized curriculum primarily focused on the students' understandings of STEM through activities, observations, interviews, assessments, reflections, and evaluations over seven weeks. Through reflection and analysis, the findings that impact STEM students' experiences, which include (a) connection to oneself to culture and STEM, (b) the need for role models who represent diversity in STEM fields, and (c) the development of tools that assist students in developing resiliency and acquiring leverage within STEM learning communities. These findings show the necessity for decolonized STEM curriculum as a starting point for STEM educators to engage students in STEM to activate their knowledge (e.g., science identity development) as a consequence of this study. Furthermore, these findings indicate that this study reveals a fundamental necessity to combine culture and knowledge in the curriculum to authentically enable students to participate in STEM. [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.]