Diversity is valued and promoted in contemporary public discourse, but on the other hand, there is a strong tendency to homogenize differences in society. The tension between diversity and homogeneity is palpable on U.S. college campuses as the number of international students has been ever-increasing. A more nuanced approach is needed to grapple with the dynamics of intercultural contact entailing cultural and linguistic diversity. This dissertation investigates the discourses, ideologies, and identity negotiation experiences of international teaching assistants (ITAs) as they engage in hegemonic diversity discourses and pedagogical practices enacted within the space of a U.S. university second language classroom. Informed by critical discourse studies, this research examines what language ideologies are embedded in ESL class designed for ITAs. With a focus on power relations, this study critically investigates how the language ideologies are practiced and influence the ITAs’ identities. This study intends to contribute to promoting changes in pedagogical practices of diversity in culturally and linguistically diverse contexts. The data were collected through ethnographic research methods including participant observation, field notes, interviews, and artifacts/documents. Fairclough’s (1992; 1995; 2003) three-tiered framework of discourse analysis was employed to analyze the linkages of the local, institutional and societal levels of discourse as regards language ideologies and identities. The findings revealed that the discourses of difference as problem were being (re)produced with ideological significance through the process of recontextualization. Intertextual chains of discourses were being made to legitimize the dominant discourses through a language policy and implementation at the institutional level. The dominant discourses were being embodied in the ESL classroom grounded in a deficit model of language learning, regimenting language use and interactions within the space. The ITAs’ cultural and linguistic differences were represented as deficit or problem through the Othering strategies of identification and categorization. Asian students were overrepresented in the ESL program, implying that the institutional label `international student’ was a euphemism for Oriental indexing the culturally and linguistically distant Others. The findings suggested that the underlying language ideologies of the diversity discourses were monolingualism, native-speaker superiority, and language standardization. Those monoglossic ideologies were undergirded by the social ideology of Otherness. With difference conceptualized as a deviation from norms, the language ideologies were practiced to homogenize or remedy the cultural and linguistic diversity. Under the restrictive ideologies, deliberate discursive choices such as joke, disclaimer, code-switching, hypothetical speech, and ventriloquizing, were made from the ITAs’ agency in revealing the hidden ideologies and negotiating their identities in response to the dominant discourses. The students’ metalinguistic awareness of their language and identities defied being represented simply as an ESL learner or international student with cultural and linguistic deficiency. The students’ criticality was substantive evidence of the contradictory diversity discourses. This study has implications for researchers studying discourse, power, and identity through a critical lens, and for educators and policy makers developing language education practices that value cultural and linguistic diversity and critical language awareness in the context of equity and diversity.