Purpose: This study aimed to uncover sexual identity development and investigate the psychiatric risks for bisexual people across mainland China, Hong Kong, and Taiwan by examining ecologically informed factors at the individual, family, and community levels. Methods: An internet-based survey was administered to 685 respondents, from June to August 2021, reached primarily through lesbian, gay, bisexual, transgender, and queer community organizations and professional networks. Participants reported their demographics, identity milestones, and psychiatric symptoms. Results: Significant birth cohort and regional differences were observed regarding bisexual identity milestones. Individuals who were older, transgender and/or nonbinary, and based in Taiwan disclosed their sexual identity more. All respondents reported clinically elevated depression and anxiety symptoms, with a majority experiencing moderately severe depression (60%) and moderate or severe anxiety (80%). Approximately half of respondents contemplated suicide in the past year. Compared with cisgender women, identifying as transgender and nonbinary assigned female at birth was significantly associated with increased depression and higher odds of suicidal ideation in the past year. Enhanced self-esteem was associated with greater well-being and decreased psychiatric symptoms. Experiencing family shame was associated with increased anxiety and depression. At the community level, living in Hong Kong was linked to lower depression and suicidal ideation compared to mainland China. The presence of an LGBT group correlated with improved psychological well-being. Conclusions: Chinese bisexual people face substantial risks for depression, anxiety, and suicidal ideation, influenced by factors including self-esteem, transgender and nonbinary gender identity, family dynamics, and community context. Significant birth cohort and regional differences in bisexual identity development exist.