Researchers in second language acquisition have claimed that the teacher-student setting of the typical L2 classroom may not provide an optimal environment for negotiation of meaning. This claim, however, has been based on quantitative analyses without examination of the actual negotiation process. From a different point of view, namely, a socioconstructivist perspective, this study focuses on how a teacher supported students during negotiations of meaning and how the students contributed to those negotiations in an intermediate ESL classroom. The findings show that the teacher’s scaffolding played a crucial role in constructive negotiations. She continuously checked the students’ levels of comprehension and searched for better ways to resolve comprehension problems. In addition, she assisted the students as they modified their utterances to resolve communication breakdowns. She also offered help by mediating the students’ successful communication between each other. For their part, the students contributed their own scaffolding to assist class members who were having difficulty comprehending and producing language during their negotiations with the teacher. Those findings suggest that collaborative negotiation of meaning between teacher and student in the classroom is rich in learning opportunities.