Interaction research that has investigated the relationship between language production and second language (L2) development has largely focused on learners' immediate responses to interactional feedback. However, other speech production processes might help account for the beneficial relationship between interaction and L2 development. The current study examines whether syntactic priming—the tendency to produce a syntactic structure encountered in the recent discourse—is associated with English as a second language (ESL) question development. The participants were intermediate-level Thai learners of English (N = 46) at a large public university in northern Thailand. In two 20-min sessions, the participants carried out communicative activities with a more advanced L2 English interlocutor who had been scripted with developmentally advanced question forms. They also completed an oral pretest and two posttests that consisted of activities similar to those carried out during the treatment sessions. The results indicated that participants who evidenced high levels of syntactic priming were likely to advance to a higher stage in the developmental sequence of ESL question formation.