This research has aimed to develop and validate a leadership inventory for successful primary schools. For this purpose, for the qualitative part of the study, purposive sampling was used, and semi-structured interviews using the theoretical saturation criterion were conducted and later transcribed with 24 successful primary school principals and key teachers in the cities of Tehran and Isfahan as informants of the research. Once the data obtained from the qualitative phase were analyzed, a list consisting of 131 items was compiled, and the study began its quantitative phase. The content validity of the tool was examined by ten experts and professors in the field of educational management from universities and the Ministry of Education. The content validity ratio presented by Lawshe (1975) was calculated for each item and then compared with the table. Six items, each measuring two areas, were separated, leading to 12 items, and eight items required revision and modification. The statistical population of the qualitative phase of the research consisted of 322 primary school principals in the city of Isfahan. The statistical sample was, using the table presented for determining sample size by Cohen et al. (2001), determined as 176, and the share for each district was determined using stratified sampling and distributed in an equal and random fashion among two groups of schools – successful and ordinary. The principals put the list to work, and 167 lists were returned, indicating a 95-percent return rate. To determine the reliability of the tool, Cronbach's alpha coefficient and combined reliability were used, and the obtained figures (0.70 to 0.94) showed the measurement inventory to be of high precision. In order to analyze the quantitative data, descriptive indicators and the factor analysis test were used, the results of which pointed out the credibility of the model and the tool.