The present study aimed to identify difficulties in writing at the beginning of educational science programmes in the Finnish Open University by analysing the students' written argumentation and use of sources at the textual level. The data were analysed using qualitative content analysis. The results showed that many students began their educational studies with weak writing competencies. While many of the problems were directly related to students' failure to explain the ideas in their sources in their own words, some problems pertained to other aspects, such as the inability to construct convincing arguments. Understanding the nature of the problems in writing encountered by beginning students in educational sciences can help teachers foster students' participation in academic discourse.