Twice-exceptional students require services that identify and serve their academic and social-emotional concerns; teacher understanding of these needs is not well-studied. Using Bandura's theory of self-efficacy and social cognitive theory, a descriptive phenomenological study was conducted to explore middle school teachers' self-efficacy beliefs and personal agency when teaching twice-exceptional learners. Van Kaam's psycho-phenomenological method was used to conduct interviews and a focus group with eight middle school teachers. Three research questions were used to examine how participants describe (a) their lived experiences teaching twice-exceptional students; (b) their self-efficacy and personal agency addressing the challenges of supporting twice-exceptional learners; and (c) strategies they implemented to meet learner needs. Using Colaizzi's seven steps, narratives were reduced to five essential themes, the importance of building relationships with stakeholders, the impact of self-efficacy beliefs and challenges to personal agency on teacher trust in decision-making for students, the impact of self-efficacy beliefs and challenges to personal agency on teacher lack of trust in decision-making for students, the challenges of effectively communicating with stakeholders, and the strategies employed providing access to all learners in advanced academic environments. Teachers with high self-efficacy value and develop relationships for student achievement; however, teachers with moderate self-efficacy may develop strong teacher-student relationships but not translate them to teacher-peers/administrators nor teacher-parent, which may negatively impact student achievement. Teacher confidence directly relates to teacher self-efficacy based on personal mastery. Teacher confidence and personal agency may be hampered by psychological security discomfort but can be bolstered by administrators and peer support. Peer support and trust reinforce self-efficacy, and confidence from administrators, parents, and student trust results in positive student outcomes. Teachers with higher self-efficacy and personal agency devise strategies for effective communication with stakeholders, ensuring positive outcomes, and implement strategies ensuring students access learning that protects their dignity. Middle school administrators should provide professional development for working with twice-exceptional students in core subjects and general education classes. Schools may consider what efforts will develop communities of trust and positive relationships engendering greater student outcomes. Suggestions for further studies on teacher-stakeholder relationships and teacher self-efficacy and personal agency are included. [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.]