Background: Neonatal danger signs are now a public health problem and contributing factors for neonatal death. Early detection of neonatal danger signs is an important step towards improving newborn survival. This study aimed to assess knowledge on neonatal danger signs and associated factors among post natal mothers in public hospitals of Addis Ababa Ethiopia.Methods: An institutional based cross-sectional study was conducted among 363 postnatal mothers at public hospitals of Addis Ababa, Ethiopia from March 15th to May 15th, 2019. Systematic random sampling technique was used to select the study participants and semi-structure interviewer administer questionnaire was used to collect the data. The data were entered by using Epi- data version 4.4.3.1 and analyzed by using bivariable and multivariable logistic regression model with SPSS version 25.0. Then statistical significance was declared at P- value < 0.05. Finally, the data was presented by using text, figures and tables.Result: All mothers expected to participate in the study were interviewed. Overall, 33.1% of mothers had good knowledge about neonatal danger signs. Factors like maternal education college and above (AOR=2.11, 95% Cl: 1.51-2.99), caesarean section mode of delivery (AOR=3.72, 95% Cl: 1.71-8.12), parity (AOR=5.34, 95% Cl: 1.64-2.64) , education during PNC follow up (AOR=2.77, 95% Cl: 1.49-5.15) and identification of skilled birth attendant (AOR= 2.25,95% Cl:1.13-4.40) were significantly associated with level of maternal knowledge. Similarly, information from health professionals (AOR=4.54, 95%Cl: 2.16-9.70) and access to television were also a statistical significant factor for maternal knowledge (AOR=2.15, 95% Cl: 1.11-4.15). Conclusion: Maternal knowledge on neonatal danger signs was poor. Therefore educational intervention during ante natal care, institution delivery and post natal care visit, advocating the use of media and increase maternal birth preparedness like identification of skilled birth attendant are highly recommended.