Background:Although antenatal care (ANC) coverage has been increasing in low- and middle-income countries, the adherence to the ANC initiation standards at gestational age <12 weeks was inadequate including Thailand. The study aimed to improve the rate of early ANC initiation by training the existing local health volunteers (LHVs) in 3 southernmost provinces of Thailand.Methods:A clustered nonrandomized intervention study was conducted from November 2012 to February 2014. One district of each province was selected to be the study intervention districts for that province. A total of 124 LHVs in the intervention districts participated in the knowledge–counseling intervention. It was organized as half-day workshop using 2 training modules each comprising a 30-minute lecture followed by counseling practice in pairs for 1 hour. Outcome was the rate of early ANC initiation among women giving birth, and its association with intervention, meeting an LHV, and months after training was analyzed.Results:Of 6677 women, 3178 and 3499 women were in the control and intervention groups, respectively. Rates of early ANC were significantly improved after the intervention (adjusted odds ratio [OR]: 1.29, 95% confidence interval [CI]: 1.17-1.43, P < .001) and meeting an LHV (adjusted OR: 2.06, 95% CI: 1.86-2.29, P < .001), but lower at 6 months after training (adjusted OR: 0.76, 95% CI: 0.60-0.96, P = .002). Almost all women (99.7%) in the intervention group who met an LHV reported that they were encouraged to attend early ANC.Conclusion:Training LHVs in communities by knowledge–counseling intervention significantly improved early ANC initiation, but the magnitude of change was still limited.