The aim of this study was to develop a valid and reliable assessment and evaluation instrument to specify the efficacy of the students in technology and design courses. The assessment instrument was composed of an item pool, experts' views about the validity scope, pre-application, analysis of structure validity and reliability analysis steps. This study was carried out with the seventh-grade students in State secondary schools in Northern Cyprus. A scale with 38 items and seven factors was determined through an exploratory factor analysis. The scale consisted of synthesis, basic application, evaluation, formal analysis, further analysis, advanced application and comprehension dimensions. The confirmatory factor analysis and the factor structures were tested. At the end of the confirmatory analysis, it was noted that the variables had acceptable goodness of fit values. A valid and reliable technology and design course self-efficacy scale was developed at the end of the study.