Translanguaging, an emergent theoretical orientation to language, has become a widely discussed topic in writing studies with the rise of translingual movement in composition. Challenging the ideologies of standardization and monolingualism, translanguaging forwards towards a pedagogy of difference and facilitates transcending the socio-politically constructed language boundaries for negotiation of meaning in writing. The pedagogical potential of translanguaging has been documented in the literature; however, its value as a rhetorical practice in the context of U.S. college composition remains largely unexamined. This mixed-methods study therefore investigated college composition instructors and students' perceptions of translanguaging in writing. The study was conducted at a mid-sized public research-oriented university in the Northeast United States during the Fall semester of 2020. The participants were composition instructors and students who completed an anonymous online survey and took part in follow-up interviews. The mixed data revealed that in many cases, instructors adopted translingual orientations to plurality and difference, whereas students maintained dominant ideologies in their views of translanguaging by prioritizing a standardized variety of English-only writing. Students' appropriateness-based approaches to language difference in writing led to serious conclusions about the perseverance of monolingualism and standard language ideologies in college composition. The results of this study suggest pedagogical implications for writing program administration and college writing instruction. Writing programs should go beyond merely accepting heteroglossia and diversity, and actively incorporate language rights into the curriculum to manifest pluralistic approaches to language usage in college composition. Writing instructors should embrace translingual pedagogies and practices to challenge students' monocentric ideological positions and make them aware of their rights to their own language in writing. To foster students' sensitivity to plurality and difference, writing instructors should model translanguaging in course design and materials. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]