Although there have been numerous instruments for assessing teacher efficacy in teaching general education students, there is a need to develop and validate an instrument that specifically assesses teachers' efficacy in teaching students with disabilities. This study constructed and evaluated the psychometric properties of the "Student Teachers' Efficacy in Teaching Students With Disabilities" (STETSD). Exploratory and confirmatory factor analyses with independent samples from two sites were conducted. A four-factor model best fit the data. A moderate positive correlation was found between the STETSD and an existing resource teacher efficacy survey; the STETSD also significantly predicted the student teachers' intentions to pursue a career in teaching students with disabilities. Implications for practice are discussed regarding the assessment of teacher efficacy in specific subjects, the use of the STETSD, and STETSD's cross-validation with in-service teachers.