Introduction: Like the broader population, people with intellectual disability (ID) experience the process of grief after loss of a loved one. However, there are a series of risk factors characteristic of this population that can hinder the development of adaptive grief, including cognitive and affective aspects. The objective of this study was to evaluate the effectiveness of a brief intervention program in people with ID to improve understanding of the concept of death, the grief processes, and adaptive attitudes. Method: A mixed method design that included a controlled, randomized research design, was used. A total of 38 people with ID participated. The variables measured were: grief, biological and cognitive concept of death. Results: The program significantly increased understanding in two dimensions of the concept of death, Inevitability and Universality, and demonstrated a greater understanding and healthier attitudes regarding death and grief. Conclusions: It is recommended that, in future research studies, education on death be worked as early as possible in people with ID, in order to prevent future pathological grief.