Background: Iodine is an essential trace element for normal growth and development of fetus body. Iodine deficiency disorder is one of the most important preventable micro nutrition deficiency problems globally. Aim of the study: Was to assess pregnant women knowledge and practice regarding prevention of iodine deficiency during pregnancy. Research design: A descriptive research design was used in carrying out this study. Setting: This study was conducted at pregnant follow up clinic at Medical Center at Benha City, Qalubia Governorate, Egypt. Sample: Simple random sample was used in this study. The total sample included 337 pregnant women. Tools of data collection:One tool was used; an interviewing questionnaire which contained three parts. Part I: Socio-demographic characteristics of pregnant women. Part II: Pregnant women knowledge about A): Iodine deficiency, B): Nutritional sources of iodine. Part III: Reportedpractices of pregnant women regarding iodine deficiency. Results: 31.8% of pregnant women had poor knowledge about iodine deficiency during pregnancy and 55.2% of them had unsatisfactory practices regarding iodine deficiency. Conclusion: There was statistically significant relation between total knowledge score of studied pregnant women and their age and income. There was statistically significant relation between total practice of studied pregnant women and their total knowledge. Recommendation: Health educational program should be developed and implemented for pregnant women about iodine deficiency during pregnancy and booklets  should be available and distributed in all maternal and child health carecenters and in all hospitals for prevention of iodine deficiency.