The purpose of the study was to determine the association of COVID-19 vaccination with changes in cycle or duration of menstruation during menstrual cycles while receiving vaccine doses. Materials and methods. The study included 200 women aged from 20 to 38 who had at least three cycles after pregnancy or after using hormonal contraception. The women were vaccinated with Pfizer-BioNTech (Pfizer) and CoronaVac (Sinovac) (Sinovac Biotech) vaccines. The distribution of women by age is as follows: 20–24, 25–29, 30–34, 35–38 years. Additional characteristics included parity (nulliparous versus parous), body mass index, which was classified as underweight or normal weight, overweight or obese; education and relationship status (sustainable relationship or not). Results and discussion. Of 200 women included in the study, 110 (55.0%) patients were vaccinated, 90 (45.0%) were unvaccinated. Average age of vaccinated was 31.6 ± 2.88 years, unvaccinated – 29.3 ± 3.05 years (t = 0.55, p = 0.584). Among 110 vaccinated women, 73.6% had regular menstrual cycles before the introduction of the vaccine during the last year, among 90 unvaccinated women, 74.4% of women had regular menstrual cycles. Menstrual irregularities among those who were vaccinated and those who did not undergo COVID-19 were 11.8% and 14.5%, respectively. Symptoms appeared within a week in 27.6%. In 62.1% of cases, symptoms appeared after the first dose, in 37.9% of cases – after the second dose. There was a significant difference between menstrual irregularities during the COVID-19 pandemic and menstrual irregularities after vaccination (p < 0.001). The study showed that 26.4% of our sample complained of menstrual irregularities after vaccination against COVID-19, especially after the first dose (16.4%). The type of vaccine did not affect the frequency of menstrual disorders in these women. After vaccination, women reported significantly longer average duration of menstruation and duration of the menstrual cycle compared to their condition before vaccination. These symptoms decreased a month after vaccination. Although 27.6% had a clinically noticeable change in cycle duration by 7-8 days, this change rapidly weakened during two post-vaccination cycles. We found no significant changes in the duration of menstruation between vaccination doses. Conclusion. Among women who received vaccines against COVID-19, 26.4% of cases had menstrual irregularities. When counseling women who have received a COVID-19 vaccine, it is advisable to inform them of the possible occurrence of temporary and self-limiting menstrual irregularities in the following months