Teachers play a key role in the optimal development of pupils with special educational needs (SEN) by providing an inclusive learning environment. Strategies used for the education of pupils with SEN are typically based on an individual educational plan (IEP). Based on extant literature, we aimed to understand (1) whether primary school teachers were involved in the preparation of the IEP, (2) the extent to which they were familiar with the adjustments written in the IEP, and (3) the significance of the role played by the IEP in a teacher’s daily work. Eighty-nine primary school teachers from different schools in north-east Slovenia participated in this questionnaire-based research. The results show that fewer than half of the teachers were always involved in the preparation of the IEP for the pupils with SEN they teach. A few reported that they had not taken part in the preparation of pupils’ IEP at all. Furthermore, just over half of participants were familiar with all the adjustments recorded in the IEP. There were also differences in the responses to the research based on the professional title and experience of the teachers. The differences were in favour of teachers with more experience and teachers with more senior professional titles. We also found that most teachers believed that an IEP plays an important role when working with pupils with SEN and writing a regular lesson plan. Our findings represent the starting point for the preparation of education for pupils with SEN and act as a basis for the self-evaluation of a teacher’s pedagogical work.