Menstruation is a phenomenon unique to the female, the onset of menstruation is one of the most important changes occurring among the girls during the adolescence years. The study was undertaken with the objective to assess the pre-test and post-test knowledge level of adolescent girls by educational intervention on menstrual hygiene & to evaluate the effectiveness of educational intervention on level of knowledge regarding menstrual hygiene among adolescent girls. Pre-Experimental with One group pretest post-test design was used to assess the Knowledge level of adolescent girls on menstrual hygiene by a structured questionnaire on menstrual hygiene. Educational intervention on menstrual hygiene was given. The findings of the present study concluded that 5(6%) adolescent girls had low knowledge and 29(38%) had high knowledge regarding menstrual hygiene. and 41 (55%) of them had average knowledge. the mean knowledge score was 16.68 in pre-test raised to 28.32 in post-test. There is a significant difference between pre-test and post-test knowledge scores of adolescent girls on menstrual hygiene.