Introduction: After COVID-19 vaccination, women of reproductive age reported changes in their menstrual cycle. Materials and methods: A retrospective study was carried out after a survey on social networks that included women aged 18–41 years with normal cycles according to International Federation of Gynecology and Obstetrics and who were vaccinated (complete schedule for two doses, except J&J/Janssen or incomplete with a single dose). Women with following conditions were excluded: pregnant or lactating women; history of diseases that cause menstrual irregularities or early menopause: anorexia, bulimia, polycystic ovary syndrome, hypothyroidism, obesity, or low weight; hysterectomized or oophorectomized patients; and high performance athletes. Results: Overall, 950 women completed the survey between July and September 2021. In total, 408 women met the inclusion criteria, and 184 reported the following characteristics: frequency (normal 43.47%, infrequent 25%, and frequent 31.53%), regularity (regular 51.08%, irregular 42.93%, and absent/amenorrhea 5.97%), duration (normal 65.21%, prolonged 26.08%, absent/amenorrhea 8.69%), and volume (heavy 41.84%, light 20.65%, and absent/amenorrhea 6.52%). Conclusions: SARS-CoV-2 infection and COVID-19 vaccination can influence the menstrual cycle and cause alterations.