Attitudes and beliefs about menstruation can place restrictions on menstruating women and girls, limiting their ability to fully participate in community life, education and employment. This paper presents evidence on menstruation-related beliefs contributing to restrictive practices in Papua New Guinea (PNG), Solomon Islands (SI) and Fiji. Focus group discussions and interviews were undertaken with 307 adolescent girls, women and men in a rural and urban site in each country. Data were analysed using an inductive thematic approach. Participants described a range of attitudes and beliefs that restrict the behaviour of menstruating women and girls. Themes include the belief that menstrual blood is 'dirty'; that when menstruating, girls and women can bring 'bad luck' to men; secrecy and shame associated with menstruation; and beliefs about the impact of certain behaviours on menstruation and health. Restrictive practices were more frequently reported in PNG and SI than Fiji, and more common in rural compared with urban sites. Some restrictions, such as avoidance of household chores, were perceived as desirable or driven by women themselves. However participants identified other restrictions, such as not being able to attend church or hygienically wash menstrual hygiene materials, as unwanted, in some cases impacting on participation in school, work and community life. Education initiatives guided by women and girls, implemented by local stakeholders and grounded in a sound understanding of specific contexts are needed to address discriminatory attitudes and beliefs that contribute to unwanted restrictions, and to support enabling attitudes and beliefs regarding menstruation.