Danger signs of pregnancies are a warning signs that women encounter during pregnancy, child birth and postpartum. It is important, to know this warning signs for women and health care providers to rule out serious complications and initiate treatment immediately. Insufficient knowledge about danger signs of pregnancy is one of the major contributing factors for maternal deaths. There is limited research on the knowledge of danger sign among the pregnant mothers in Arbaminch town. Therefore, this study was intended to assess the knowledge of danger sign of pregnancy and associated factors among ANC attendant pregnant women in Arbaminch town governmental institutions. Institution based cross-sectional study design was conducted from October, 22/2016 G.C to November, 27/ 2016 G.C. A systematic random sampling technique was used to select study participants from pregnant mothers attending ANC during the time of data collection. Data was collected using structured questionnaire and it was entered in to EPI Data version 3.1 software program and exported to SPSS version 20 software for analysis. Descriptive analysis and chi square test was done for association and p-value < 0.05 has been considered as significant. Result has been presented in tables, graphs and figures. A total of 358 pregnant women were included in the study with a response rate of 100%. The study indicate that 68.4% of the respondents had knowledge on danger signs of pregnancy and there was an association with the knowledge on danger signs of pregnancy and the age of the respondent, educational status of the respondent, monthly income, marital status, history of previous pregnancy, discussion about pregnancy issues, place of delivery of the previous birth, and attendants of the previous delivery.