Purpose: Ethiopia is one of the sub-Saharan countries most affected by high maternal and infant mortality. The government has trained health extension workers (HEWs), the community health workers, to deliver preventive and basic curative health services to community residents in Ethiopia. Very few studies have investigated on-the-job educational effects for HEWs on improvement of their knowledge and performance confidence in maternal and child health care (MCH). This study aimed at identifying the educational effects for HEWs in one health center in Tigray, Ethiopia on improvement of their knowledge in MCH. Methods: Twelve HEWs from 6 health posts participated in this study. A health center officer provided a total of 5 educational sessions on antenatal and postnatal care, family planning, and newborn care from August, 2012 to April, 2013. Ten to 12 items regarding the topics were tested before and after each education. Wilcoxon signed rank test was used to analyze the data. Results: All the HEWs were female with average 4-year working experience. Their knowledge significantly increased after education, except the first session. Their satisfaction on education was greater than 45 points out of 50. Conclusion: This study suggests a focused education for HEWs should continue to improve their capacity on MCH.