Background: Pfizer vaccine has been approved for use in Saudi Arabia. Although the vaccine efficacy has been frequently addressed, little knowledge is available regarding the real-world post-vaccination menstrual disturbances. Objective: The aim was to evaluate the possible association between Pfizer vaccine and the post-vaccination menstrual irregularities among Saudi citizen and resident women. Subjects and methods: A self-administered validated questionnaire was used to obtain the data. It was distributed all over Riyadh City, KSA through social media and 731 females responded to the survey. Results: Overall, 50.9% of the participants reported a menstrual change after vaccination, in particular, those who received the 2 doses. There was a significant and positive correlation between the number of doses and the experience of menstrual changes being associated with the 2 dosed women. In details, 60.5% mentioned a menstrual delay, 30.4% reported early onset, and 9.1% mentioned a menstrual change other than in the date. 43.3% reported a decrease in the amount of menstrual flow, 34.9 % mentioned an increase. 62.4% declared an increase in the severity of pain while 11% reported a decrease. Interestingly, only 60.8% of the respondents mentioned the persistence of the menstrual changes each following cycle. However, the changes were positively correlated with the age and negatively associated with the marital status being less in married. Conclusion:  It was concluded that the post-vaccination menstrual changes might be related to the age, marital status, and those receiving 2 doses and these changes could be related to the immune response frequently associated with vaccines.