Background: since the emergence of COVID-19 vaccinations, many women around the world have reporting abnormalities in their menstrual periods post-vaccination. Aim: to determine the relationship between COVID-19 vaccines and menstrual cycle characteristics among nursing students Design: Descriptive design was used. Setting: this study was conducted at the Faculty of Nursing Helwan University Sample: A Purposivesample of 150 female nursing students in the first and second academic year 2022-2023 Tools: Two tools used to collect data .Tool (1): A Structured interviewing questionnaire included demographic characteristics, medical history, COVID-19 vaccines of the subjects, menstrual characteristics of the subjects .Tool (2):Menstrual characteristics post COVID-19 vaccine Results: The majority of the female students had no change in the number of days between two consecutive periods, about one third had change in the length of their menses and menstrual flow, more than two third experienced no change in amount of blood, the majority of them had no amenorrhea or spots between menses after vaccination. However, minority of female students experienced dysmenorrhea, with half restoring to pain-relief medication Conclusion: COVID-19 vaccines had minimal effect on menstrual characteristics among female nursing students , both of age and the type of COVID-19 vaccine received appeared to be associated with variations in menstrual cycle characteristics, early menarche was significantly associated with greater post vaccination menstrual alterations Recommendations: Development of educational programs targeting female nursing students to provide accurate information about the potential effect of COVID-19 vaccination on menstrual cycles.