To determine the effectiveness of the Contra Caries Oral Health Education Program (CCOHEP) for improving low-income, Spanish-speaking parents' oral health knowledge and behaviors for their young children. Mexican American children in the United States suffer disproportionately high prevalence and severity of early childhood caries, yet few evaluated, theory-based behavioral interventions exist for this population. CCOHEP is a theory-based curriculum consisting of four 2-h interactive classes designed for and by Spanish speakers and led by designated community health educators (promotoras). Topics included children's oral hygiene, caries etiology, dental procedures, nutrition, child behavior management, and parent skill-building activities.Low-income Spanish-speaking parents/caregivers of children aged 0-5 years were recruited through community services in an agricultural city in California. Survey questions from the Oral Health Basic Research Facts Questionnaire measuring oral health-related behaviors and knowledge were verbally administered before, immediately after, and 3 months after attendance at CCOHEP. Five questions measured aspects of parental toothbrushing for their children (frequency, using fluoridated toothpaste, brushing before bed, not drinking or eating after nighttime brushing, adult assistance), three questions measured other oral health behaviors, and 16 questions measured oral health-related knowledge. Analyses of within-person changes between pre- and post-tests and again between post-test and 3-month follow-up consisted of McNemar's test for binary outcomes and sign tests for ordinal outcomes.Overall, 105 caregivers participated in CCOHEP (n = 105 pretest, n = 95 post-test, n = 79 second post-test). At baseline, all parents self-reported doing at least one aspect of toothbrushing correctly, but only 13% reported performing all five aspects according to professional guidelines. At post-test, 44% of parents reported completing all aspects of toothbrushing according to professional guidelines (P < .001). Statistically significant improvements were seen in 4 aspects of toothbrushing (P ≤ .008) between pretest and post-test (all but adult assistance). The second post-test showed 3 of these improvements were maintained, while adult assistance and the other reported behaviors improved (P ≤ .008). Between pretest and post-test, checking child's teeth monthly and frequency of sweet drinks consumption improved (P ≤ .008), while frequency of eating sweet foods did not change. Knowledge was high at baseline (mean 12.8 of 16), but 6 knowledge items improved significantly between pretest and post-test. Improvements were maintained at second post-test.Contra Caries Oral Health Education Program improved low-income Spanish-speaking parents' oral hygiene knowledge and self-reported behaviors for their young children, and change was sustained 3 months after the end of the intervention. Future, more rigorous evaluation of the intervention is recommended.