Background: Maternal obesity and gestational diabetes mellitus (GDM) contribute to increased risk for type 2 diabetes mellitus (T2DM) among both mothers and their offspring. Randomized trials demonstrated T2DM risk reduction in adults following lifestyle behavior change and modest weight loss; the evidence base for at-risk children remains limited. Purpose: Evaluate the feasibility, acceptability, and preliminary efficacy of a T2DM prevention intervention for mother-child dyads delivered by Federally Qualified Health Center staff. Methods: A group randomized design tested the effects of a behavioral lifestyle intervention on T2DM risk factors in women with a history of GDM and their 8- to 12-year-old children. Mother-child dyads were recruited and randomized to intervention or wait-listed control conditions. Intervention participants completed the 13-week intervention; control participants received standard of care. Baseline and 13-week measures assessed program acceptability and feasibility, and explored effects on body weight, waist circumference, hemoglobin A1c, and lifestyle behaviors. Results: Forty-two dyads were randomized and 35 (83%) completed pre-/post-measurements. Participants and program leaders positively rated content and engagement. Nearly all strongly agreed that activities were enjoyable (97%), applicable (96%), useful (97%), and motivational (96%). Attendance averaged 65% across 2 cohorts; delivery costs were approximately $225/dyad. There were no significant differences in body weight, BMI (or BMI z-score), waist circumference, hemoglobin A1c, diet quality, physical activity, sleep, or home environment changes between intervention and control groups. Conclusions: A family T2DM prevention program was feasibly delivered by FQHC staff, and acceptable to mothers and children. Program efficacy will be evaluated in an adequately powered clinical trial.