This study investigated Principals’ Decision-Making Styles for Effective Administration of Public Senior Secondary Schools in Rivers State. Two research questions and two hypotheses were used for the study. The correlational research design was used for this study. The population of the study consisted of all the 7, 142 teachers in the 276 Secondary Schools in the 23 Local Government Areas of Rivers State.  The sample of this study comprised 714 teachers (respondents) in 24 public senior secondary schools in Rivers State, representing 10 percent of the total population of the study. The simple random sampling technique was used for the study. The questionnaire instrument titled: “Principals’ Decision Making Styles and Effective School Administration Questionnaire” (PDMSESAQ) was used for the study. The questionnaire were divided into two sections:  section A was for collection of demographic data while section B contained 30 items on principals’ decision-making styles for effective administration of Public Senior Secondary Schools in Rivers State.  Furthermore, the coefficients index value obtained was 0.75 and therefore the reliability of the instrument was established. Data gathered from this study were collated and statistically analyzed.  The statistical tool used for answering the research questions were Mean and Standard Deviation statistics while the null hypotheses were tested using ANOVA associated with the regression analysis at 0.05 Alpha level of significance. The findings of this work revealed that principals’ decision-making positively influence effective administration of Public Senior Secondary Schools in Rivers State. The conclusion of the study is that decision-making styles should be used integratively with elements of biases of each. The study therefore, among others recommend that principals should be able to appraise a particular situation before using any decision-making styles in the administration of public secondary schools in Rivers State.