The global demands for greater understanding of the challenges menstruating school girls face and the associated potential risks and consequences are growing. This study was launched to investigate the knowledge, attitudes and practices of menstruating school girls on menstrual hygiene, and the environmental school challenges affecting menstrual hygiene management (MHM.) Stakeholders' involvement in MHM promotion in schools was also assessed. Qualitative and quantitative data were collected in 12 schools randomly selected from both rural and urban communities in three geo-political zones in Nigeria. Qualitative methods included focus group discussion for mothers, girls and boys; in-depth interviews for in-school and out of- school girls; and key informant interviews for school principals, teachers, and participants from the Zonal Directors' of Education, Chairmen States' Universal Basic Education Board and Chairmen School Based Management Committee /Parents Teachers Association. A structured observation checklist was used to ascertain the conditions of the school environment and the WASH facilities in the schools. A total of 152 activities with 394 participants were conducted. Findings from this study showed that menstruating school girls in Nigeria faced many challenges which affected their ability to manage their menstruation in a dignified and hygienic way. The key findings cut across religion and ethnicity and were related to various beliefs and cultures. The findings showed that availability and adequacy of WASH facilities, adequacy and flow of Information on MHM and access to materials for hygienic management of menstruation all impacted girls' experience of menstruation.