PURPOSE: The purpose of the study was to describe, compare, and examine associations at baseline of reproductive health awareness, knowledge, health beliefs, communication and behaviors related to gestational diabetes (GDM) and GDM risk reduction in a vulnerable population of both American Indian/Alaska Native (AIAN) adolescent girls and their mothers. METHODS: Descriptive/comparative/correlational analyses examined multitribal baseline data on 149 mother-daughter (M-D) dyads (N = 298; daughter age = 12-24 years) enrolled in a longitudinal study to adapt and evaluate a culturally relevant diabetes preconception counseling (PC) program (Stopping-GDM). The associations between GDM risk reduction awareness, knowledge, health beliefs, and behaviors (eg, daughters' eating, physical activity, reproductive-health [RH] choices/planning, M-D communication, daughters' discussions on PC) were examined. Data collected online from 5 national sites. RESULTS: Many M-D lacked awareness/knowledge of GDM and risk reduction. Both M-D were unaware of the girl's risk for GDM. Mothers' knowledge and beliefs on GDM prevention/RH were significantly higher than daughters. Younger daughters had greater self-efficacy healthy living. Overall sample reported low to moderate scores for both M-D communication and daughters' GDM and RH risk-reduction behaviors. CONCLUSIONS: Knowledge, communication, and behaviors to prevent GDM were low in AIAN M-D, especially daughters. More than daughters, mothers perceive greater risk of GDM for daughters. Early culturally responsive dyadic PC programs could help decrease risk of developing GDM. Implications for M-D communication is compelling.