OBJECTIVES: To determine effects of the 5-4-3-2-1 Go! community social marketing campaign on obesity risk factors. METHODS: We randomly assigned 524 parents of 3- to 7-year-old children to receive 5-4-3-2-1 Go! counseling or not. We surveyed parents about 5-4-3-2-1 Go! behaviors and perceptions of children's behaviors at baseline and one year later. We conducted multivariable logistic regression for each outcome. RESULTS: Parents who received counseling consumed more fruits and vegetables at follow-up (OR 1.749, [95% CI: 1.01-3.059]). Parental exposure to messaging at children's school events was associated with higher water consumption (6.879, [1.954-24.212]). CONCLUSIONS: 5-4-3-2-1 Go! is a promising intervention.