Background: Understanding and practicing menstrual hygiene is crucial for women’s health globally. Unsafe menstrual hygiene practices (MHP) contribute to a lower quality of life. In impoverished nations, gender inequity, societal norms, cultural taboos, poverty, and inadequate facilities hinder meeting menstrual health demands. The study aimed to assess the level of knowledge and practice of menstrual hygiene among adolescent girls in Mangalore Taluk, Dakshina Kannada, Karnataka. Methods: A cross-sectional study was conducted among 482 adolescent girls from government high schools in Mangalore Taluk. A cluster random sampling technique was adopted to select the schools and complete enumeration was done from each school with the aid of a semi-structured questionnaire. The data was analyzed by using SPSS v-23. Descriptive analysis showed frequency and percentage, and logistic regression explored associations between menstrual hygiene practices (MHP) and demographic variables. Results: Out of 482 participants, 82.3% got primary menses information, mostly from mothers (77.8%). About 48.5% had average menstruation knowledge, and 76.8% followed proper MHP. Urban areas showed 4.368 times higher MHP practice than rural areas, revealing a significant relationship. Conclusions: Study finds Mangalore high school girls generally maintain average menstrual hygiene practices. It is very important to set up suitable disposal facilities in schools and to organise awareness campaigns on good menstrual hygiene habits. Thus, it contributes to improving quality of life.