Context: Adolescent-mothers communication on reproductive health (RH) is a strategy to decrease risky behaviors. Objective: This study aimed to find out the desire, level and content of communication between adolescents and their mothers. Methods: A cross-sectional study was conducted from Oct 2015 to March 2016. Patients: Six hundred fifth adolescent’s girls in Mazandaran high schools were selected via stratified sampling method. Intervention: The level of communication between adolescents and their mothers and having problems in it, intention to discuss with mothers and knowledge on RH were assessed Main Outcome Measures: Questionnaires including socio-demographic characteristics of the sample and their knowledge on RH and also two cultural adapted standard questionnaires including The Parent- Adolescent Scale and RCT’s Initiating Discussion. Results: The level of communication between adolescents and their mothers (34.12± 6.10) and being problems on it (31.83± 4.31) and intention to discuss with mothers (7.58± 4.17) was weak. The main topic of discussion between girls and their mothers was about puberty (83.7%) and then sexual relationship (15.5%), contraception (11.4%) and marriage (9.7%). The maximum time of discussion was 5-10 minutes (33%) within the six months (35.5%).About one third of girls satisfied on communication with mothers (34.5%) and felt comfortable talking with them about RH (31.3%). The mean score of adolescent’s knowledge on RH was also 5.76±1.45 of 10. Conclusion: Most adolescents did not communicate with mothers about RH and their knowledge on it also was weak. Strange adolescent-mothers communication and solve their barriers should be concern. It is need to sensitize both adolescents-mothers on the importance of having communication on RH issues and encourage them to involve in adolescents RH programs and design intervention.