The overall aim of this doctoral thesis was to deepen and inform the maltreatment prevention possibilities for adults with intellectual and developmental disabilities (IDD) across the lifespan. The first three studies approached maltreatment prevention from the vulnerability assessment perspective, whereas the last study provided a more in-depth focus on prevention at an individual level. Study I focused on the cross-cultural validation of a self-report measure assessing social vulnerability in adults with ID: the Social Vulnerability Test-22 items (TV-22). Participants were French-speaking adults with ID (n=29). Results indicated that the TV-22 is a reliable and valid measure for assessing social vulnerability in adults with IDD. Study II reported findings related to the implementation of the TV-22. This study used a mixed-method design to assess the implementation outcomes of the TV-22: the acceptability (e.g., the complexity of coding), the appropriateness (e.g., the usefulness of the test), and the assessment fidelity of the TV-22 by special education practitioners (n=31) were measured. Results underscored the importance of evaluating implementation outcomes when a new measure is developed to ensure its correct use by stakeholders. Using the test validated and implemented in the first two studies, Study III aimed to further the understanding of social vulnerability in adults with IDD, more specifically in digital risks. Participants were adults with ID (n=51). Participants’ answers to the five items of the TV-22 related to digital risks were qualitatively analyzed. Results highlighted the importance of designing, in a comprehensive manner, preventive measures against the victimization of people with ID. Study IV described the development of a curriculum, in English and in French, to prevent elder abuse in adults with IDD (n=10). It deepened the current information on the prevention of abuse of personswith IDD across the lifespan by providing new information on the prevention possibilities of abuse among elder adults, an area of research that was, until present, scarce. Overall, this doctoral thesis provides theoretical and practical advances in our understanding of maltreatment and its prevention in the IDD population across the lifespan. Findings open research perspectives regarding social vulnerability, its similarities across countries, and its relation to cognitive sub-skills and adaptive behavior; they also propose new avenues for future research on preventing the maltreatment of elders with IDD.