Infant and under five mortality in developing countries has declined in the past two decades while the new born mortality has not significantly changed. Most neonatal death take place at home, this indicate that lack of early recognition on the danger sign and low treatment seeking behavior of mothers (care taker) towards modern health care service. The objective of this study is to assess knowledge of mother on danger signs of neonatal and postnatal illness and health seeking behavior among pregnant and postpartum mother in Gedeo Zone, 2014/15. A community based cross-sectional study design, supplemented with qualitative study is conducted. The study period is done from 1/11/2014-30/11/2014 and the study populations is all sampled pregnant and postpartum mothers who live in Gedeo Zone during study period. Sample size is determined by Level of significance (0.05), Power (0.50), Proportion of Knowledge of newborn danger signs on Mother’s response was 29.3% according to a study result in SNNPR which result in sample size of 318.Considering design effect of 2 and adding 10 % for non-response rate, the final sample size is 700. Focus group discussion and in-depth interview was conducted with pregnant and postpartum mothers and health care provider respectively and triangulated with quantitative findings. The sampling procedure will involve a multistage stratified cluster sampling technique. A total of 700 respondents were included in the study and giving 100% response rate. The mean ages of the respondent was 25.8 (SD± 8) with a range age of 17 to 40. Marital Status of the respondent showed that 15(2.1%) were single followed by 655 (93.6%) were married & 12 (1.7%) were Widowed. Bivariate analysis showed that significant associations between treatment seeking behaviour of mother’s from health center to new born with residence, educational status of mother & husband, income, family size, perception score towards new born health problem, ethnicity, affordability & accessibility and place of delivery however, the result of the multivariate analysis showed that, Residences, educational status of the respondent, delivery and family size were predictors of treatment seeking behaviour of mother’s from health centre to new born. Residences, educational status of the respondent, delivery and family size were predictors of treatment seeking behaviour of mother’s from health centre to new born thus as a recommendation appropriate health education intervention should be given to the respondent.