The present study is aimed to investigate in-service bilingual teachers' perceptions of training needs in the competences and knowledge required to implement bilingual curricula in Taiwan. To this end, this study used mixed methods consisting of questionnaires and individual interviews to collect data from the intended cohort, that is, in-service teachers involved in bilingual curricula at elementary and junior high schools in Taiwan. In this study, data collection comprised questionnaire data from 76 respondents and transcripts of 15 interviews. Descriptive statistics and Grounded Theory method were employed to analyze the research data. The study revealed the differences in training needs of Taiwanese in-service bilingual teachers with regard to the school levels, teacher types, language proficiency levels, and bilingual teaching experiences. From the findings, several suggestions are made for professional development for in-service bilingual teachers in Taiwan. It is suggested that Taiwan's Ministry of Education consider the factors of teacher types and school levels when developing in-service training courses. Additionally, training on the English language needs to be re-evaluated in the professional development courses for bilingual teachers in Taiwan, in particular for English language teachers. Through this study, the author wishes to shed light on training needs of bilingual teachers in Taiwan, and accordingly, to propose suggestions on bilingual teacher training.