Helminthiasis is a popular health problem in Indonesia especially in children. Knowledge on helminthiasis prevention has a great role in overcoming the disease. The purpose of this research is to know the effectivity of health education in increasing knowledge level of elementary school teacher on helminthiasis. This research uses experimental design and pre-post study method. Data collection is done in Jakarta on October 12th, 2011 by asking 67 elementary school teachers to fill a before and after questionnaire. The questionnaire consists of five questions about helminthiasis prevention, including ascariasis, trichuriasis, and oxyuriasis. From the result, knowledge level of respondent before health education are as follow: 17,9% good, 31,3% average, and 50,7% poor. After health education, the knowledge level are as follow: 58,2% good, 35,8% average, 6,0% poor. Before health education, the question least understood by the respondent is when to give medication to a person with helminthiasis (only 6,0% answers right). Based on marginal homogeneity test, there is a siginificant difference (p<0,01) on the knowledge level before and after health education. It is concluded that health education is effective in increasing knowledge level of elementary school teacher on helminthiasis prevention.