Understanding what motivates first-generation doctoral students (FGDS)—whose parents or primary caregivers did not attend college—is critical for improving graduate retention. While prior research has examined first-generation undergraduates, less is known about FGDS in the social and behavioral sciences. Guided by Self-Determination Theory and Relationships Motivation Theory, this study analyzed interviews with 18 sociology PhD students (9 FGDS, 9 continuing-generation doctoral students [CGDS]). FGDS emphasized relatedness rooted in community commitments, whereas CGDS prioritized autonomy and competence through research goals. Sociology served as a motivational conduit for both groups. Findings inform admissions, mentorship, and institutional supports that promote equity and persistence.