Research in mathematics education among d/Deaf and hard-of-hearing (DHH) students has documented that DHH students lag behind their hearing peers on measures of mathematics achievement. The discrepancy is attributed to multiple factors, including mathematics instruction that focuses on skill and computation. Research focused on mathematics identity has great potential for advancing understanding of mathematics teaching and learning among DHH students by providing insight as to how current curricula, activities, and instruction do and/or do not benefit the learners. In this study, I examined the mathematics learning experiences of a group of DHH middle-grade students in a self-contained classroom. I drew upon theories of mathematics identity to examine what it means to do mathematics and to be a competent mathematics learner in this classroom. The general and mathematical obligations that emerged involved expectations of behaviors and proficiencies in the context of low-level mathematics activities. The characterizations of competence were based, in part, on jointly constructed expectations in the classroom. I present case-study analyses of two students, Anna and Vivian, to illustrate how the obligations and characterizations of competence, coupled with the students' mathematics experiences and perceptions of d/Deafness, shaped how these students saw themselves and were seen by others as learners and as doers of mathematics. Anna's experiences in the self-contained DHH mathematics classroom contributed to her beliefs that DHH individuals can be, and are, successful in mathematics. Vivian's experiences mainstreamed in the general education mathematics classroom contributed to her beliefs that she and all DHH learners are less competent in mathematics, compared to hearing learners. Several new and related questions emerged with implications for practice and further research.