He used to lecture at the Faculty of Science (PMF), Academy of Fine Arts, Music Academy, Academy of Dramatic Arts, Faculty of Humanities and Social Sciences, and other Universities in Croatia. Since 2009, he has been working (full time) at the Faculty of Teacher Education, University of Zagreb, holding the title full professor, and from 2018 in the capacity of Dean of Faculty. He teaches courses at the undergraduate, graduate, and doctoral levels of study. The areas of his scientific and research interest are the following: research methodology (social science), quantitative methodology, and statistics. He has been a mentor to a dozen students who are in the process of preparing their master's or doctoral thesis. Sinisa Opic is the author of many scientific and research papers and he reviews many international papers. He has been an invited lecturer, president, and keynote speaker at many world international conferences. Additionally, as a visiting professor, he taught at the University of Brock (Canada), University of Ljubljana, University of Maribor, University of Mostar (BIH), and Macquarie University (Australia). University of Sankt Gallen (Swiss), University of Barr Ilan (Israel), University of Graz (Austria), Houston University (USA)...