The main purpose of the study is to develop a "Facebook Effect Scale on Teacher Quality" (FESTQ) based on the pedagogical content knowledge, technological pedagogical content knowledge and lifelong learning frameworks. Study participants comprised 556 teachers. Explanatory factor analysis and confirmatory factor analysis were conducted in the development and testing of the FESTQ. The results showed that the FESTQ is reliable and valid to measure Facebook effect on teacher quality. The FESTQ consists of 40 positive six-point Likert-type items along with six factors, "instructional knowledge for in-class applications," "general culture knowledge," "individual characteristics," "instructional knowledge related to student characteristics," "instructional knowledge for preparing an assessment tool" and "special content area knowledge." The psychometric properties of the FESTQ, the study limitations and suggestions for future studies are discussed.