The coronavirus COVID-19 pandemic is the global health crisis of our time and the greatest challenge we have faced since World War II. Pregnant women are considered to be a high-risk group for severe acute respiratory syndrome coronavirus infection, and the potential adverse effects of the virus on maternal and perinatal outcomes are of concern. One of best ways to avoid these potential adverse effects is to provide the women with knowledge to improve awareness. Mobile application is the brightest hope to provide accurate practical knowledge by nurses who have a key role in the management of pregnant women during pandemic crisis. Aim: evaluate the effect of the instructional organized sessions via a mobile-based application on pregnant women's knowledge, practice, and attitude toward COVID-19. Research design: A quasi-experimental study design was utilized. Setting: antenatal outpatient's clinics, obstetrics, and gynecological hospital, at El-Manial Maternity Hospital – El Kaser Aliniy, Cairo University, Egypt. Methods: A convenience sample of 200 pregnant women regardless the gestational age was recruited for the study. Tools: Data collection tools included five tools: Maternal Structured Interview questionnaire; Knowledge, practices, and attitude assessment questionnaires about COVID-19 and pregnant women's satisfaction regarding instructional method. Results: The result of the study revealed that there were statistically differences in the total mean score of knowledge, practice and attitude after receiving instructional organized sessions via Mobile-based application compared to before intervention. Conclusion: The findings of the study support the research hypotheses that pregnant women who received instructional organized sessions via Mobile-based application showed a positive effect on level of knowledge, practice and attitude as compared to before intervention. Recommendations: Government agencies in the healthcare sector should reinforce more effective primary preventive measures and policies by developing mobile-based applications to provide quality and safety information that can help in flattening the curve of this pandemic.