This study examined the effects of collaborative dialogue in learning the speech act of request. Seventy-four second-grade girls' junior high students were divided into three groups. The "collaborative group" (n = 25) received explicit metapragmatic information on request (request head act and modifications) followed by a dialogue construction task in pairs. The "individual group" (n = 25) received the same information but completed the same task individually while thinking aloud. The last group, control group (n = 24), did not receive instruction. During-task interaction in the collaborative group and think-aloud protocols in the individual group were audio-recorded. Instructional effect was measured by a discourse completion task (DCT). Target request head acts in DCT were scored, and request modifications were analyzed for frequency. The collaborative group outperformed the individual group on the production of the head act at immediate post. No group difference was found in request modifications. Analysis of interaction and think-aloud data showed that the collaborative group produced the target head act more successfully than the individual group, but no group difference was found in the use of modifications.