Problem Statement: Science, technology, engineering, and mathematics (STEM) education has recently become a remarkable research topic, especially in developed countries as a result of the skilled workforce required in the fields of the STEM. Considering that professional tendencies are revealed at early ages, determining students' interest in STEM careers is important for Turkey's workforce. The question, "How can Turkish middle school students' interest in STEM careers be determined?" constitutes the problem statement of this study. Purpose of the Study: The aim of this study is to adapt the STEM Career Interest Survey (STEM-CIS), which is a type of 5-point-Likert scale, into Turkish. The survey consists of 44 questions, and includes science, technology, mathematics, and engineering sub-dimensions. Method: Items were independently translated into Turkish by the authors after necessary permissions were received. Afterwards, the authors reached a consensus about the Turkish meanings of each items. The items were reviewed and edited by English and Turkish field experts to ensure validity. The survey was administered to 1,033 middle school students (grades 5-8). The data were analyzed by the Confirmatory Factor Analysis (CFA) in the AMOS program. The reliability of the scale, as well as its sub-dimensions, was calculated in the SPSS program (Cronbach's alpha and Mc-Donald's omega). To test criterion validity, correlation values were calculated between scores of the STEM-CIS and Interest in Science Scale (ISS). The test-retest method and item analysis were carried out. Also corrected item-total correlation values were determined. Findings: A scale, which consists of 40 items and four sub-dimensions including science, mathematics, engineering, and technology, was obtained as a result of the analysis. The Cronbach's alpha internal consistency coefficient was calculated as 0.93 for the whole scale, 0.86 for the science sub-dimension, 0.88 for the technology sub-dimension, 0.94 for the engineering sub-dimension, and 0.90 for its mathematics sub-dimension. Conclusion and Recommendations: The scale adapted into Turkish can be used to assess middle school students' interest in science, technology, mathematics, and engineering careers. However, each sub-dimension of the scale can also be administered separately to determine middle school students' interest.