The aim of this study is to analyze the peer and self-assessments of higher education students' oral presentation skills with the many-facet Rasch measurement model and to determine students' opinions on peer and self-assessment. In the study, convergent parallel method, one of the mixed-method research approaches, was used. The study group consisted of 11 university students studying at a state university in the 2022-2023 academic year. The FACETS program was used to analyze the data. The three facets identified in the study were the assessee (11 students), the assessor (11 students) and the items (16 items). Therefore, 11 participants scored (peer and self-assessment) on a 16-item assessment form. In addition, students' opinions on peer and self-assessment were obtained through three open-ended interview questions prepared by the researcher. According to the results of the study, it was determined that there was a statistically significant difference between the students in terms of their oral presentation skills, between the assessors in terms of their strictness/generosity in scoring, and between the criteria (items) in terms of the level of difficulty in realization. In addition, the participant opinions obtained from each interview question were analyzed through themes and sub-themes formed according to the general thoughts on peer and self-assessment, experiences, and whether the participants considered themselves as a reliable rater or not. In terms of practice, it can be suggested to provide detailed and enlightening information to students before peer and/or self-assessment in the classroom environment, and to give quick feedback to those who have not done the assessment appropriately. In addition, the reasons for the biases identified in peer and self-assessments in the current study can be investigated in future studies.