The literature has revealed the impact of personal factors on feedback-seeking behavior (FSB) in second language (L2) writing. However, little is known about how teacher academic support influences FSB in L2 writing and whether this relationship is mediated by L2 writing self (ideal and ought-to L2 writing selves). To address the lacunae, this study used a quantitative research design and a sample of 221 Chinese non-English major undergraduates to explore the relationships among teacher academic support, L2 writing self, and FSB. Structural equation modeling (SEM) analysis revealed that teacher academic support could directly predict the two dimensions of FSB (feedback monitoring and feedback inquiry) and L2 writing selves. Moreover, mediation analysis indicated that teacher academic support indirectly predicted both dimensions of FSB via ideal L2 writing self, and it also indirectly predicted feedback monitoring via ought-to L2 writing self. This study suggested that teacher academic support, as an environmental factor, could enhance learners' writing motivation and self-regulated writing behaviors. Pedagogical implications for L2 writing instruction were discussed.