This study examined the relationships between writing motivation and written composition performance in Chinese among 388 Chinese children in Grades 3 to 5 in accordance with the framework of self-determination theory. Multiple regression analysis results showed that writing motivation measures (external regulation, introjected regulation, identified regulation and intrinsic motivation) contributed a unique variance to written composition performance before and after controlling for the contribution of cognitive-linguistic skills important to written composition (i.e., word dictation, working memory and syntactic knowledge). Identified regulation was the only significant predictor of written composition performance. These results are discussed with reference to the impact of Chinese culture on motivation to write among Chinese children.