Introduction: Early initiate into complementary feeding is initiation of complementary feeding before six months. The first two years of life are a critical window of opportunity for ensuring optimal child growth and development. Nutritional deficiencies during this period can lead to impaired cognitive development, compromised educational achievement. Improving infant feeding practices is therefore critical to improved nutrition, health, and development. Objective: To assess the prevalence of early initiation of complimentary feeding and associated factors among mothers of an infant with 9 months age in public health institutions at immunization clinics of Finote Selam town, North-west Ethiopia, March - May 2021. Methods and materials: The study was conducted in public health institutions at immunization clinics of Finote Selam town from March - May 2021. An institutional-based cross-sectional study was conducted by taking a sample size of 374. Systematic random sampling was used to select the study participant visiting Finote Selam public health institutions for expanded programmed of immunization service. All public health institutions in the study area were included in the study. A descriptive statistic was used to present frequency of categorical variables. Bivariable logistic regression model was used to identify the association of independent and dependent variables. Then variables with P-value less than 0.25 in the bivariable logistic regression analysis was entered to multivariable logistic regressions statistical analysis. Finally, Adjusted Odds Ratio (AOR), 95% Confidence Interval (CI) and P < 0.05 were used to claim statistical significance. Results: It was found that the prevalence of early initiation of complementary feeding before sixth month was 19.8% (95% Cl: 16.0,24.1). Poor knowledge mother AOR (5.246(2.856-9.635)), having maternal illness at post-natal period AOR (3.933(1.793-8.628)), presence of cow in the house hold AOR (2.296(1.062-4.962), mothers who have no postnatal care follow up for their child in Health service AOR (2.836(1.545-5.204)) were significantly associated factors for early initiation of complementary feeding in the study area. Conclusion and Recommendation This study showed that early initiation of complementary feeding in the study area was lower than the critical point of the national prevalence and that is good. The determinates of were mothers who has no PNC, and mothers who encountered medical illness at post-natal period, having poor knowledge, having cow in the household were significant predictors for early initiation of complementary feeding in which all of them are modifiable factors. Therefore, mothers should be encouraged to have postnatal care follow up and, awareness creation, counseling should be done on society by concerned bodies on recommended six-month duration of exclusive breastfeeding was recommended. Key words: Complementary feeding, cross-sectional study, Finote Selam public health