The aim of this research is to develop the scale of self-knowledge forlearning English. The research population consists of all the ninth-gradestudents receiving education in Anatolian high schools of the Aydın city in theacademic year 2015-16. For the first pre-implementation, the sampleof the study includes 646 ninth class students in five Anatolian high schoolsin a province of Aydın. Following the analyses, the scale was revised. For thesecond pre-implementation of the revised scale, a different sample in anothertwo provinces of Aydın was determined, and the sample included 816 ninth gradestudents receiving education in eight Anatolian high schools in total, fourschools for each one of the two provinces in the same academic year. After theanalyses of the first pre-implementation and second pre-implementation dataseparately, it was determined that, the scale developed consists of a total of17 items and those items were grouped under the four factors identically inboth analyses. Regarding to the factors' percentages in explaining totalvariance of the scale; the percentages are 19% for metacognition, 17% for motivation, 13% for anxiety and 12% forendeavor. It was identified that all these factors together contribute to thevariance of the scale with a percentage of 61%. Key to the confirmatory factoranalysis carried out after the explanatory factor analysis, the fit indiceswere examined altogether, and the model was determined as acceptable overall.In the analysis carried out to determine the internal consistency coefficientsof the scale, Cronbach Alpha reliability coefficient was found to be 0.81 forthe whole scale. This indicated that the items of the scale are consistent witheach other. Internal consistency reliability coefficients determined for thefactors respectively are; 0.84 for metacognition, 0.85 for motivation, 0.72 forendeavor and 0.70 for the fourth factoranxiety. In accordance with the results obtained in the study, the scale can beused as a valid and reliable instrument to measure ninth class students'self-perceptions for learning English.