Background: Menstruation is a central part of the everyday life of most women, and menstrual attitudes may impact health and well-being. Objectives: This article aimed to map menstrual attitudes among adult women and examine factors associated with these attitudes, such as aspects of menarche and current menstruation, and rarely studied factors, such as genital self-image and sexual openness. Study Design: A cross-sectional online survey. Method: A sample of 1470 women, aged 18–50 years, were recruited through social media sites. The Menstrual Self-Evaluation Scale was used to measure three different attitudes: menstruation as natural, shameful, and bothersome. Multiple linear regression analysis was used to investigate the relationship between each attitude and factors related to menarche and current menstruation, contraceptive use, genital self-image (assessed by Female Genital Self-Image Scale), and sexual openness ( Personal Comfort with Sexuality Scale). Sociodemographic variables were included into the models as covariates. Results: Agreeing with the attitude of menstruation as something natural was predicted primarily by positive emotions at menarche, experiencing less menstrual pain, using no or nonhormonal contraception, and having a positive genital self-image. Perceiving menstruation as bothersome was predicted by a lower educational level, experiencing stronger menstrual pain, having more perimenstrual psychological symptoms, and using hormonal contraceptives. Menstruation as something shameful was chiefly predicted by lower sexual openness and a negative genital self-image. Conclusion: Many women held attitudes about menstruation as both something natural and bothersome. Menarche and current menstruation experiences, and contraceptive method, played central roles in shaping attitudes toward menstruation as natural and bothersome. Viewing menstruation as shameful stood out from other attitudes by indicating a triad of self-objectified shame that includes menstruation, sexuality, and genital self-image. Further research into the relationships between menstruation, contraceptive use, sexuality, and body image is needed to enhance our understanding of women’s menstrual health.