The impostor phenomenon is "a psychological experience of intellectual fraudulence where one struggles to internalize successes, instead attributing personal accomplishments to chance, luck, or trickery" (Clance, 1985). Through this dissertation study, Guthrie and four co-researchers, Mindy, Bobbie, Rosalie, and Lisa, explored the complicated relationships between the impostor phenomenon, graduate students, and their perceptions of graduate program writing and writing mentorship. In the first phase of the study, Guthrie surveyed 431 graduate students across the disciplines to measure their impostor feelings and learn about their perceptions of graduate-level writing and mentorship. In the second phase, Guthrie operationalized the impostor phenomenon by defining and then constellating 1) Graduate students' disruptive dispositions (individual, internal qualities that impact knowledge transfer) towards writing and mentoring; and 2) Additional factors that influenced students' impostor experiences. Implications for graduate-level writers include propositions that 1) Disruptive dispositions can work together to impact writing and 2) Dispositional knowledge is an important domain for writing expertise. Implications for mentoring graduate-level writers include arguments for 1) The importance of explicitly raising conversation with mentees about the impostor phenomenon and 2) Graduate-level writing and revision should be structured within learning communities where novices and experts learn together and avoid isolated practices as much as possible. [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.]