Objective: The aim of the present research is to compare puberty problems in adolescent girls with and without mild mental retardation (MMR) in Tehran. Method: In this analytical and cross- sectional research, 90 subjects with MMR, and 90 subjects with normal condition were chosen using method of cluster random sampling. The Child Behavior Check list (CBCL) performed to investigate behavioral problems and in order to study sexual problems a researcher-made questionnaire was used. Results: The  analyses indicated that rate of anxiety, depression, social problems, attention problems, internalizing and sexual problems in period of puberty in girls with MMR are greater than the normal group. On the other hand, no significant difference was found on somatic complaints, thought problems, delinquent behavior and externalizing between the 2 groups. Conclusion: This research could unfold some important aspects of behavioral and sexual problems in adolescent girls with MMR.