Chinese language abilities are crucial assets to the development and well-being of children living in a Chinese community, where Chinese is used as the medium of everyday communication and school instruction. However, as the most widely used logographic language in the modern world, Chinese is difficult for both first and second language learners to master. There is also a lack of applied work on how to promote the Chinese learning of young children, especially those from ethnic minority families. Therefore, the present study used a cluster randomized controlled trial to evaluate the effectiveness of the C-for-Chinese@JC Program in promoting the Chinese language abilities of both Chinese and ethnic minority children. Using kindergartens as clusters, 480 Chinese children and 347 ethnic minority children from Hong Kong, China, were randomly assigned to undertake the C-for-Chinese@JC Program (218 Chinese and 190 ethnic minority children) or join the wait-list control group (262 Chinese and 157 ethnic minority children). In pre- and posttests, children completed tasks on orthographic knowledge, phonological awareness, morphological awareness, vocabulary knowledge, story retelling, word reading, and word writing in Chinese. Repeated-measures mixed-group ANOVAs indicated that Chinese children who had undertaken the program showed faster growth in all outcome measures except for orthographic knowledge. Meanwhile, ethnic minority children who had undertaken the program showed faster growth in all seven outcome measures. Findings highlighted the utility of a theoretically informed, developmentally appropriate, and culturally responsive approach to improve the Chinese language acquisition of both first- and second-language learners.