To understand the role of early intervention (EI) practitioner confidence in the use and application of assistive technology (AT), a 24-item Assistive Technology Confidence Scale (ATCS) was developed and distributed to EI personnel. This article reports on the development and psychometric properties of the ATCS and the relation between scores on the ATCS, years of experience, education, and overall practitioner self-efficacy. Analyses revealed that the ATCS is a reliable measure of AT confidence in three service domains: application and use of AT, AT assessment, and accessing information about AT and AT resources. EI practitioners with more than 10 years of experience were more confident in AT service provision than EI practitioners with less experience. The ATCS was positively related to overall EI practitioner self-efficacy. Implications for the application of the ATCS for EI research and training are discussed.