Objective: Α gap seems to exist in research concerning the implementation of Social Emotional Learning interventions for students with disabilities in special education schools. The aim of the particular paper, within the framework of a broader research, is to highlight the multiple applications of Achenbach System of Empirically Based Assessment (ASEBA) in a SEL Intervention in a Special Education School in Greece. Method: A mixed-method research design was applied, as with the combination of quantitative and qualitative methods the weak points of each method are compensated separately. In this paper, though, only the assessment process through ASEBA is going to be presented, so as to point out its multiple applications. In this multiple case study 3 teachers and a parent of each of the 3 students participated. Findings: So, an overall improvement was perceived concerning the behavior of all students, although different perceptions were noticed e.g. in terms of context, as it became evident in the social validity measures. Implication for Practice and Research: ASEBA is a valuable tool for screening procedure, assessing behavior change and social validity in SEL interventions through its multi-informant approach, detailed subscales and normative data. our findings contribute to both in-service and novice teachers’ or researchers’ knowledge about how to use a multipurpose tool like Achenbach System of Empirically Based Assessment (ASEBA) in the assessment process of a SEL intervention program. Furthermore, an important aspect of our article is that social validity is addressed, which is quite sidelined in research and in practice, even though it constitutes a crucial aspect of any intervention program.