Abstract Background Knowledge of danger signs of obstetric complications is first step in the appropriate and timely referral to essential obstetric care. Although women’s knowledge about the obstetric danger signs is important for improving maternal and child health, little is known about the current knowledge and influencing factors in pastoral community of Ethiopia. This study, therefore, aims to fill this gap by assessing the current level of knowledge and associated factors of pregnant women living in Erer district of Somali region, Ethiopia. Methods A community based, cross-sectional study was conducted from April 7 to 21, 2014. The study involved 666 pregnant women residing in the district. Two-stage sampling technique was used to select the study subjects. Data about women’s socio-demographic information, reproductive history, knowledge of the danger signs, exposure to media and interventions were collected by interviewer administered questionnaires. A respondent who spontaneously mentioned at least two of the danger signs during each of the three periods was considered knowledgeable; otherwise not. Descriptive, bivariate, then multivariable logistic regression were done. Results Six hundred thirty two pregnant women were interviewed with a response rate of 94.9 %. Only 98 (15.5 %) respondents were knowledgeable about obstetric danger signs. Urban residence [AOR = 2.43; 95 % CI (1.40, 4.21)], women who had been pregnant five or more times [AOR = 6.65; 95 % CI (2.48, 17.89)] and antenatal care utilization [AOR = 5.44; 95 % CI (3.26, 9.09)] were associated with being knowledgeable about obstetric danger signs during pregnancy, childbirth and postpartum. Conclusion A significant proportion of pregnant women in Erer district do not have knowledge of obstetric danger signs. The implication is that lack of recognition may lead to delay in seeking care. Area of residence, gravidity and antenatal care service utilization are independently associated with the knowledge of women on obstetric danger signs in Erer district, a pastoralist community. Thus, intervention programs aiming to improve women’s knowledge about obstetric danger signs and symptoms should consider the factors independently associated.