Quality vocational education is the foundation of social and economic development. Quality assurance of the vocational education system is therefore an important task of all stakeholders in the system, with quality being assured at all levels and involving all stakeholders. The national system of vocational education quality assurance in the Republic of Croatia is linked with the European Quality Assurance in Vocational Education and Training. It is established at the level of vocational education institutions (vocational schools) and at the level of qualifications, and it is based on the processes of self-assessment and external evaluation. Self-assessment in vocational schools is monitored and evaluated by a quality assurance committee, with school stakeholders being involved in its implementation. This doctoral dissertation aims to examine self-assessment as a segment of vocational education quality assurance. The subject of the research is the analysis of the existing selfassessment system in vocational schools and of the stakeholders’ attitudes on self-assessment, the process of implementation and the relevance of quality parameters. The empirical research included two research tasks and was implemented in two parts, using two different methods, instruments and data collection processes, on a sample appropriate for each research method. The first task was related to the analysis of the existing selfassessment system of vocational schools, the technical implementation in schools and reports and results of the self-assessment implemented in the school year 2017/2018. Results of the review of school documents (statute, school curriculum, school annual plan and programme and annual self-assessment report) in 27 sampled vocational schools confirmed the existing differences in the technical implementation and in the results of self-assessment of vocational schools implemented in the school year 2017/2018. The second task was related to the survey and analysis of the attitudes of the respondents, stakeholders of vocational schools with different roles in the self-assessment process, on self-assessment, the implementation process and the relevance of quality parameters in the self-assessment process. Results of the analysis of the questionnaires received from 402 respondents in 27 sampled vocational schools showed clear attitudes on self-assessment and confirmed the difference in the attitudes of the respondents who are educated and participate in the management of the self-assessment process in a vocational school compared to the respondents who do not have that role. The process of self-assessment of vocational schools can be implemented following a set and „imposed“ legal obligation, however, the culture of self-assessment of schools can be built only if teachers, experts and all other school stakeholders are highly trained and educated. The quality of vocational education can be ensured by implementing the process of self-assessment at all levels: from the self-assessment of students, teachers and principals to the self-assessment of vocational schools and the self-assessment of the entire vocational education system. The self-assessment of vocational schools is an important segment of quality assurance in the vocational education, and the precondition to implement it successfully is to have quality methodology and the adequate training and education of all school stakeholders.