Purpose: English and Mandarin are the 2 most spoken languages in the world, yet it is not known how stuttering manifests in English-Mandarin bilinguals. In this research, the authors investigated whether the severity and type of stuttering is different in English and Mandarin in English-Mandarin bilinguals, and whether this difference was influenced by language dominance. Method: Thirty English-Mandarin bilinguals who stutter (BWS), ages 12-44 years, were categorized into 3 groups (15 English-dominant, 4 Mandarin-dominant, and 11 balanced bilinguals) using a self-report classification tool. Three 10-min conversations in English and Mandarin were assessed by 2 English-Mandarin bilingual clinicians for percent syllables stuttered (%SS), perceived stuttering severity (SEV), and types of stuttering behaviors using the Lidcombe Behavioral Data Language (LBDL; Packman & Onslow, 1998; Teesson, Packman, & Onslow, 2003). Results: English-dominant and Mandarin-dominant BWS exhibited higher %SS and SEV scores in their less dominant language, whereas the scores for the balanced bilinguals were similar for both languages. The difference in the percentage of stutters per LBDL category between English and Mandarin was not markedly different for any bilingual group. Conclusions: Language dominance appeared to influence the severity but not the types of stuttering behaviors in BWS. Clinicians working with BWS need to assess language dominance when diagnosing stuttering severity in bilingual clients.