This study explores the process of becoming-scientist-with, a dynamic and relational concept that redefines science identity development as a nonlinear, evolving journey. Focused on a Black male student, Travis, the study examines how his science identity was shaped through entanglements with various material and discursive forces across multiple science, technology, engineering, math, and medicine (STEMM) learning spaces. Becoming-scientist-with is conceptualized as a continual negotiation of identity within these environments, emphasizing the roles of power, systemic racism, and institutional practices in shaping students' experiences. The paper critically examines Travis' journey through an undergraduate biology program, a research immersion program, and an afterschool STEMM club, showing how exclusionary practices in formal educational settings and affirming practices in informal contexts shaped his persistence in STEMM. The findings highlight the significance of supportive relationships, culturally responsive mentorship, and alternative learning environments in disrupting institutionalized racism. Ultimately, the study argues for a reimagined approach to science identity that accounts for the fluid, contested, and coconstructed nature of becoming a scientist. By recognizing science identity as a process of becoming-scientist-with material and discursive forces within STEMM learning spaces, the study embraces an ethical commitment to equity, advocating for more inclusive and affirming spaces in STEMM education to support marginalized students.