The aim of this study is to review the opinions of principals and teachers on TUBITAK-4006 (Scientific and Technological Research Council of Turkey) science fairs which are organized in about 10.000 schools every year in Turkey. This study is a qualitative research and it is formed with phenomenological design. The study group is determined with criterion sampling method, and it comprises 10 teachers and 10 school administrators who have participated in TUBITAK-4006 science project fairs. The data are collected with a semi-structured interview form, and the interviews are carried out face to face. The data collected have been evaluated using content analysis method. As a result of the analysis, the viewpoints of the school administrators and teachers are presented in two themes and seven categories. For the both participant groups, the themes are analysed by categorizing them as the effects on teachers, the effects on students and parents. Besides, the suggestions category is indicated under one single title. According to the findings, all the participants stated that TUBITAK-4006 science project fairs are useful if carried out considering their purposes while they cause more harm when their objectives are disregarded.