Background: Timely identifying people with intellectual disabilities in need of palliative care is important. Therefore, we developed PALLI: a screening tool for deteriorating health, indicative of a limited life expectancy. Here, we aimed to describe development of PALLI and to explore its applicability. Method: We used a five-stage mixed-methods procedure to develop PALLI based on knowledge from practice. For exploring applicability, professionals caring for people with intellectual disabilities completed PALLI for 185 people with intellectual disabilities and provided information on applicability after 5-6 months. Results: The final version of PALLI included 39 questions relevant for people with intellectual disabilities. Applicability was adequate: Most professionals found PALLI relevant and reported no ambiguous questions. Added value of PALLI was reflecting on and becoming aware of the process of decline in health. Conclusions: PALLI shows promising applicability and has potential as a tool for timely identifying people with intellectual disabilities who may benefit from palliative care.