<i>Background</i>: Pregnancy is a normal process that results in a series physiological and psychosocial changes that can be accompanied by some danger signs and complications which are potentially life threatening to the mother and/or foetus. Although, childbirth is positive expectation for most of the women, it can be problematic for others. Knowledge of obstetric danger sign is essential first step in accepting and for motivating women to seek health care service with appropriate and timely referral to comprehensive obstetric and new-born care. <i>Objective</i>: This study was aimed to assess knowledge of obstetric danger signs and associated factors among pregnant women attending ANC clinic in Jigjiga public health institution, Somali, Ethiopia, 2019. <i>Method</i>: Institutional based cross-sectional study design was conducted in Jigjiga Public Health institution from April 15 to 31, 2019. A Systematic random sampling technique was used to select a total of 399 study participants using single population proportion. Data was collected using a pre-tested and well-structured questionnaire. Data was coded, entered and cleaned in Epi-Data version 6.04 and then exported into SPSS statistical software version 20 for analysis. Descriptive statistics were used to determine sociodemographic, obstetric characteristic, health & health related variables and knowledge of obstetric danger sign while bivariate & multivariate logistic regression was used to identify factors associated with knowledge of obstetric danger signs. <i>Result</i>: Out of 399 Respondents, 164 (41.1%) were knowledgeable regarding all type of obstetric danger sign during Pregnancy, Childbirth and Postpartum; The most frequently key obstetric danger signs identified by participants were sever vaginal bleeding during the pregnancy 64.2%, childbirth 57.4% and postpartum 50.4%; Formal education [AOR: 2.297, 95% CI (1.274, 4.143)]; Antenatal care service visit [AOR: 4.226; 95%CI (2.256, 7.918)]; PNC utilization visit [AOR=5.256, 95% CI (2.879, 9.595)]; history of obstetric complication [AOR: 4.273; 95% CI (2.042, 8.944)] and other related factors like Maternal Occupation, home visit, Mass media access and husbands a companion during health facility visit were statistically significance associated with being knowledgeable about obstetric danger signs. <i>Conclusion and Recommendation</i>: A significant proportion of pregnant women were not knowledgeable about obstetric danger signs at all categories which may result lack of delay in seeking health care service. Increasing level of awareness, health education, home to home visit and support women’s health seeking behaviour and encouraging husband to support women’s during health care visit may help women to recognize obstetric danger sign and seek health care services.