Objectives: We evaluated an education, distribution, and fitting program for increasing age-appropriate and correct child restraint use. Methods: We performed a cluster randomized trial involving 28 early childhood education centers in low socioeconomic status areas in Sydney, Australia. The main outcome was optimal restraint use defined as age-appropriate restraints, installed into the vehicle correctly and used correctly. Results: One service withdrew after randomization, so data are presented for 689 child passengers, aged 3 to 5 years, from 27 centers. More children attending intervention centers were optimally restrained (43% vs 31%; P =.01; allowing for clustering). More 3-year-olds were using forward-facing seats rather than booster seats, more 4- to 5-year-olds were using booster seats instead of seat belts alone, and there were fewer errors in use at intervention centers. Among non-English-speaking families, more children attending intervention centers were optimally restrained (43% vs 17%; P =.002; allowing for clustering). Conclusions: The program increased use of age-appropriate restraints and correct use of restraints, which translates to improved crash injury protection. Multifaceted education, seat distribution, and fitting enhanced legislation effects, and the effect size was larger in non-English-speaking families.