The main purpose of this study was to investigate the effectiveness of Principals’ leadershiprnin some selected secondary schools of Addis Ababa City Administration. To this end, bothrnqualitative [case study] and quantitative [descriptive survey] approaches were applied inrnthis study. Primary data were gathered from Principals, vice principals, department heads,rnteachers, sub city education office heads and supervisors, and PTSAs of the selectedrnSchools and analyzed using both descriptive and inferential statistics, i.e. percentiles, meanrnscores, and standard deviation. Additionally, qualitative data were collected from schoolrnprincipals, sub city education office heads, and supervisors through interview, and fromrnParents, Teachers, and Students Association (PTSA) through focused group discussions.rnQualitative data were analyzed after the responses were transcribed using respondents’ ownrnwords and categorized in to various themes and subthemes. It was found out thatrneffectiveness of schools principals’, in setting goals, developing vision, forming strongrnfunctional relationship among the school community, and showing professional endeavorsrnin inspiring teachers do their work enthusiastically was below the desired level. The studyrnfurther revealed that lack of adequate training and experience related to the functions ofrninstructional leadership, high staff turnover, shortage of resources and more engagementrnon routine works that had less value to the schools’ vision and mission were some of thernmain problem hindering principals’ leadership effectiveness. Accordingly, it is concludedrnthat almost all of the school principals were not effectively leading core activities of theirrnschools by forming communal cooperation among the staff within the school, on one hand,rnand collaboration between the staff of the schools and the community outside the schools, onrnthe other hand. Finally, it is recommended that responsible parties including Addis AbabarnCity Administration Education Bureau (AAEB) are advised to fill the knowledge and skillrngaps of the principals by designing and providing long and short term professional trainingrnand development programs on: strategic instructional leadership, effective cooperative andrncollaborative school leadership styles as well as internalization of the selection criteria asrnstipulated in “A Blue Print for Teachers Development Program†in a suitable manner