Water borne infections are among the most emerging and re-emerging infectious diseases throughout the world. Water borne diseases are infectious diseases spread primarily through contaminated water. Though these diseases are spread either directly or through flies or filth, water is the chief medium for spread of these diseases and hence they are termed as water borne diseases. Water contamination is caused by sewage and industrial effluents, surface runoff and many anthropogenic activities that alter the physical (color, taste, and smell) and chemical characteristics of water. Aim of the Study-Aim of the study was to assess the effectiveness of computer assisted planned teaching on knowledge regarding selected water borne diseases and its preventive measures among mothers of under five children in selected area at Etawah (U.P.) Methodology- Quantitative research approach was used for the present study .Quasi experimental design was used for present study.Setting of the study was Baidpura, Saifai, Etawah and Heonra, Etawah .Population of the present study are Mothers having under five years children, residing at Baidpura, Saifai, Etawah and Heonra, Etawah. Sample consist a total number of 100 subjects (Mothers) who were having children below 5 years of age residing in Baidpura, Saifai, Etawah and Heonra, Etawah . Simple Random Sampling technique by lottery method was used for the present study.Result- result found that the effectiveness of Computer assisted teaching regarding knowledge of Water borne disease and its prevention among mothers of under five children. It shows that there is significant improvement in the level of knowledge, after the computer assisted teaching programme, The pretest mean knowledge score is (52.7%) and post test mean knowledge score is (84.6%) On an average, mothers are gained 31.9% of the knowledge than pretest. Conclusion-. This study shows a significant knowledge gain among the mothers of under five children regarding computer assisted planned teaching on water borne diseases.