Background: The risk of Venous thromboembolism is to a great extent during pregnancy and the early postpartum period. Risk assessment, Clinical factors, and investigation of Venous thromboembolism during these times should integrate pregnancy-specific risk factors and postpartum considerations. Aim of the study aimed: investigate the effect of the structured in-service training program on Improving Nurses' performance Regarding Venous thromboembolism (VTE) prophylaxis during pregnancy and postpartum.  Study Design:  A quasi-experimental (one group pre-test post-test) design.  Setting: The study was conducted in the obstetrics and gynecology departments. The hospitals involved in this study are (Al Salam Hospital, June Thirty Hospital, and Port Fouad Hospital, Port Said City, Egypt. Subjects: Convenience sample consisting of 141 nurses in this study. Tools of data collection: Structured interviewing questionnaire regarding Antenatal, intrapartum and postpartum Venous thromboembolism; an observational checklist; the standard instrument used to assess the barrier regarding performing the Venous thromboembolism prophylaxis during pregnancy and postpartum period and satisfaction tool. Results: A highly statistically significant improvements in all items of total knowledge of the studied sample before and after the intervention regarding the Venous thromboembolism risk factors, manifestation and investigations. Also, a highly statistically significant improvements in all items of the total knowledge of a studied sample before and after the intervention regarding the Venous thromboembolism prevention. Moreover, a statistically significant improvements in all items of the total practice and attitude of the studied sample before and after the intervention regarding the prevention of venous thromboembolism. The lack of professional competencies besides the work conditions challenges seems to be the main barriers that prevent the studied sample from performing Venous thromboembolism prophylaxis in the clinical area. Moreover, the research results show that the participating nurses were highly satisfied with current in service training program.Conclusion: The in service training program gain its anticipated results as the studied nurses' knowledge, practice and attitudes towards the venous thromboembolism prophylaxis during pregnancy and postpartum will be improved after the implementation of the in-service training program. Recommendations: Whereas a professional in-service training program affects the patient outcome and inpatient services. It is important to give the education chance to the nurses to attain new professional in-service education regarding venous thromboembolism.