This study aimed to investigate self-beliefs of 11th grade students in a mathematics PBL classroom (n = 47). The data were collected over a period of five weeks during the second semester of the 2018 academic year using students' self-construal questionnaires, students' self-efficacy questionnaires, students' observation forms, students' reflection forms, the teacher's notes, and students' interview forms. Descriptive statistics (percentage, mean, and standard deviation) and descriptive analysis were used to analyse the data. It was found that students in a PBL classroom showed positive self-beliefs in the dimensions of self-construal and self-efficacy.