Latinos make up the fastest growing ethnic minority group in the United States and are at higher risk for the developmental of internalizing symptoms in adolescence than other ethnic groups (Merikangas et al., 2010). Rumination has been identified as a transdiagnostic risk factor associated with several internalizing disorders such as depression, anxiety, and comorbidities of the two (McLaughlin & Nolen-Hoeksema, 2011; Nolen-Hoeksema et al., 2008). Further, indicators of the hypothalamic-pituitary-adrenal (HPA) axis (i.e., flatter diurnal cortisol slopes [DCS] and greater cortisol awakening responses [CAR]) are associated with greater risk of internalizing disorders and chronic stress (Adam et al., 2010; Adam et al., 2017). Notably, no studies have examined the association between rumination and the diurnal cortisol slope in Latino populations, and literature on the relation of rumination and the CAR is mixed (Cropley et al., 2015; Hilt et al., 2017; Zoccola et al., 2011). Leveraging self-reported rumination as well as gold-standard salivary cortisol collection procedures (Stalder et al., 2016), the current study sought to elucidate associations between daily rumination and diurnal cortisol in an adolescent Latino sample by examining gender differences and bicultural competence as potential moderators of this association. Results indicated a significant but small association between night-before rumination on problems/stress and next-day DCS. Further, gender differences were detected in the effects of same-day rumination and the CAR. Greater rumination on feelings was associated with a smaller CAR the same day in males, while greater rumination on problems/stress was linked with a greater CAR the same day in females. In addition, there were no buffering effects of bicultural competence. Findings inform future research regarding potential bidirectional relations of daily rumination and the CAR, as well was how different kinds of daily rumination may have differing associations with the CAR of males and females.