This study aims to investigate 10th grade students' agency and authority in a mathematics problem-based learning (PBL) classroom. The participants were 40 Grade 10 students. The data were collected during January-February of 2019 from twelve PBL lesson plans, Agency and Authority Observation Forms, Teacher's Notes, Students' Reflections and Students' In-Depth Interview Forms. The Agency and Authority Observation Forms were adapted from Schoenfeld and Floden (2014). The researchers found that all of the students' agency and authority dimensions in all steps of the PBL process were observable. The overall level of each dimension was at a high level.