This mixed method research was to develop and validate an instrument to measure paraeducator self-efficacy for paraeducators who work with students with disabilities. This research study's framework was DeVellis' (2017) scale instrument development process conducted in three phases: item development, scale development, and scale evaluation. The instrument was piloted with a sample of paraeducators at K-12 public schools. Instrument items were developed and aligned to the Council for Exceptional Children (CEC) (2022) seven Core Competencies for Special Education Paraeducators: 1) professional learning and ethical practice; 2) learner development and individual learning differences; 3) special education services and supports in the learning environment; 4) assessment; 5) instructional supports and strategies; 6) social, emotional, and behavioral supports; and 7) collaboration with team members. The development of this instrument to measure self-efficacy of paraeducators who work with students with disabilities will direct educational leaders, general education, special education, and researchers to further examine current inclusive practices with the aim to strengthen the paraeducator workforce. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]