Libraries have traditionally been involved in educating and supporting scientific process. However, the spread of the open science concept has led to changes in the way libraries support science. Promoting open science among various members of the society is an integral part of this change. Based on pre-viously identified competences necessary for such participation, as well as the structural-functional model of forming the librarian-bibliographer popularizer of open science competences, the course of professional development was organized in SPSTL SB RAS. The purpose of the article is to present the results of training the librarians at the professional development course “Librarian- Bibliographer - Instructor of Open Science”. Two tasks were associated with the achievement of the goal: 1) to clarify the level of preparedness of library professionals to popularize open science, and 2) to determine the usefulness of the course by comparing the level of preparedness of library professionals and professionals who graduated from the advanced training program. Based on the survey of the 4th year Bachelor of Library and Information Science graduates of 11 universities of Russia, and a survey of professionals working in libraries completed in December 2024, it was determined that library professionals have difficulties in organizing activities within the framework of citizen science and in complying with current legal regulations in the area of copyright and related rights. The advanced training course “Librarian-Bibliographer – Open Science Instructor”, developed to close the gaps in the erudition of library specialists, according to the results of the analysis of final testing of students and their comparison with the obtained data, showed the increase in the level of competences necessary for a librarian- bibliographer to popularize open science.