Available evidence indicates that despite previous efforts done by government and other education stakeholders, performance of girls in science subjects is still poor among community secondary schools in Tanzania. This study sought to investigate socio cultural factors contributing to poor performance of girls in science subject in community schools in Misungwi District. The study employed descriptive survey design whereby a total of 124 participants from five community secondary schools in Misungwi district were involved. Data collection was achieved through the use of interview, questionnaire, and documentary review. SPSS program and Microsoft office excel were the tools used to analyze Quantitative data while Qualitative data was analyzed thematically and some presented in direct quotes. The main findings of this study indicated that among other reasons the common socio-cultural factors contribute to poor performance of girls in science subjects are gender stereotype, cultural bias in which boys are favored in education than girls, forced marriage, low regard for the value of female life, heavier domestic chores at home, patriarchal social system, gender discrimination, lack of role model to girls in the society and payment of dowry to girls while still in school. It is recommended that the government, school administrations and other education stakeholders to provide education to the society to stop cultural practices that undermine girls in education, encourage parents to demonstrate good parental care to their daughters and reduce domestic chores after class hours to enable them conduct serious private studies at home. Also similar study should be conducted in different areas because this study was specific to Misungwi District.