Healthy Dads Healthy Kids (HDHK) was the first program internationally to specifically target overweight and obese fathers to improve their children's health. In previous randomized controlled trials, HDHK generated meaningful short-term improvements in the adiposity, physical activity, and eating behaviors of both fathers and children. The aim of this dissemination trial was to evaluate the 12-month impact of HDHK when delivered by trained facilitators across four low socioeconomic and regional communities in the Hunter Region, Australia. The study was a nonrandomized, prospective trial with minimal eligibility criteria (i.e., father body mass index [BMI] ≥ 25 kg/m2 and children aged 4-12 years). HDHK included eight weekly practical and theoretical sessions. Assessments were baseline, 3 months (post-intervention), 6-months, and 12-months. The primary outcome was fathers' weight. Secondary outcomes included child BMI z-score and validated lifestyle behavior measures (e.g., physical activity, diet). Overall, 189 fathers (mean age: 40.2 years, BMI: 32.6 kg/m2) and 306 children (mean age: 8.1 years) participated in one of 10 HDHK programs in four areas. Intention-to-treat linear mixed models revealed a significant mean reduction in fathers' weight at post-intervention (-3.6 kg, 95% confidence interval: -4.3, -2.9), which was maintained at 12 months (71% retention). Corresponding improvements were also detected in children's BMI z-score and a range of lifestyle behaviors for both fathers and children. Attendance and satisfaction levels were high. Positive intervention effects observed in previous randomized controlled trials were largely replicated and sustained for 12 months when HDHK was delivered by trained local facilitators in underserved communities. Further investigation into the key systems, processes, and contextual factors required to deliver HDHK at scale appears warranted.