In keeping with the international trend towards inclusive education and a context-sensitive approach to students' needs, Portugal enacted, in 2008, a law that stipulated the use of the International Classification of Functioning, Disability and Health for Children and Youth (ICF-CY) to inform special needs assessment and eligibility procedures. The necessity of conceptual and practical adjustments in the use of the ICF-CY brings up the need for training programmes that can properly prepare regular and special education teachers. This paper examines the impact of an in-service training for teachers on using the ICF-CY for describing the functioning profiles of students supported by special education services. A 25-hour in-service training was developed focusing on the biopsychosocial and person-environment fit perspectives of the ICF-CY framework. To evaluate the effects of training, 236 descriptions of functioning profiles--produced before and after the in-service training--were compared. Results showed that the model adopted in the in-service teacher training course contributed to the enhancement of teachers' skills in describing more comprehensive functioning profiles of students, reflecting a dynamic perspective among the ICF-CY components. Specifically, teachers were more able to describe the impact of the environment on student's functioning, identifying facilitators and barriers that may inform the definition of strategies in Individualized Education Programs.