ABSTRACT Background Treatment outcomes for functional communication, and for generalisation across languages and linguistic levels, remain mixed for bilinguals with aphasia (BWAs). Most studies on rehabilitation of BWAs report impairment-based approaches for participants with two broad similar Indo-European languages, but it remains unclear whether benefits extend to the untreated language or linguistic levels when the BWA speaks linguistically dissimilar languages. Furthermore, outcomes for communication-based approaches, where the components mirror everyday conversations and functional communication more closely, have rarely been examined in BWAs. Aim To examine the efficacy of Better Conversations with Aphasia (BCA), a dyadic communication-based treatment, in Mandarin for BWAs – direct treatment effects on conversations, impact on functional communication and emotional well-being, and generalisation both within and across languages. Methods Two Mandarin English-speaking bilingual adults with non-fluent aphasia (mild–moderate-to-severe) and their communication partner (CP) received BCA conducted in Mandarin for 1–1.5 h twice-weekly sessions over 10 weeks. The frequency of facilitators and barriers in conversation samples, questionnaires on functional communication and emotional well-being, a picture description task, and confrontation naming of nouns and verbs in both treated and untreated languages, were all assessed at baseline, post-treatment, and post-maintenance. Results Facilitators and barriers - Both BWAs and their CPs showed significant decreases in barrier-behavior frequencies, but P01 also showed a significant reduction in the use of facilitators. Functional Communication/Well-being - P01 reported positive effects for functional communication and emotional well-being, but P02 reported negative effects for both. No significant changes in the CPs’ ratings of the BWAs’ functional communication. Discourse - P01’s Mandarin narrative production showed no significant improvement but speech rate and efficiency improved for English picture descriptions. P02’s Mandarin picture descriptions contained significantly more words produced at a slower speech rate while significant gains in meaningfulness and efficiency were found in her English descriptions. Single-word - P01 showed improved confrontation naming accuracy for nouns (Mandarin only) and verbs (Mandarin and English), whereas P02 only showed significantly increased accuracy for verbs in English. Conclusions BCA treatment for two Mandarin English-speaking BWAs replicated earlier reports of positive direct treatment effects for monolingual PWAs, particularly the reduction of behaviors that hinder conversation success. Moreover, the generalisation, both within and across linguistically dissimilar languages, provides evidence for shared language networks that could be exploited by clinicians working with BWAs. The potential impact of culture, family context, linguistic structures, and cognitive deficits, on treatment outcome is also discussed.