For most multilingual students, knowledge and language development takes place without major difficulties. However, if this development deviates from what is expected, the difficulties need to be investigated, and support measures implemented. Complex causes interact when multilingual students need special educational support. The research fields of multilingual education and of special needs education must be taken into consideration. Unfortunately, because of the gap between these two fields, many multilingual students in need of special educational support fall between the cracks. For these students, heritage language teachers (hereafter HLTs) constitute an important link between Swedish school culture and home culture and they bear responsibility in defining the special educational support measures for these students. Therefore, through the narratives of HLTs, this study aims to gain a deeper understanding of their perception of multilingual students in need of special educational support. The present study is based on qualitative methods for collecting and analysing data. After a purposeful selection, 13 individual in-depth interviews were conducted. Thereafter, the transcriptions of the interviews were analysed thematically. The results indicate that the HLTs characterise multilingual students whose behaviour or language development deviates from the norm regarding the need of special educational support. The HLTs define linguistic deviations, the underlying causes, and the support measures needed similarly. However, behavioural deviation and the underlying causes are perceived differently, depending on the individual HLTs’ personal experiences, backgrounds and levels of education. To meet the multilingual students’ SEN in a more scientifically based approach and a more holistic way, the study discusses the need for structural changes facilitating interdisciplinary collaboration between HTL and SEN teachers, a more uniform educational path for HLTs as well as better information to special needs teachers about the roles and tasks of HLTs. In conclusion, the gap between the research fields of multilingual students’ learning and special needs education should be tightened.