This study focused on prospective memory in persons with intellectual disability and age-matched controls. Persons with intellectual disability have limited prospective memory function. We investigated prospective memory with words and pictures as cues at encoding and retrieval. Prospective and episodic memory was estimated from Prospective Memory Game performance. Pictures at retrieval were important for prospective memory in particular in the intellectual disability group. Prospective memory performance imposed a cost to Episodic Memory (ongoing task) performance in the intellectual disability group. This group was outperformed by the control group on working memory, time reproduction, time concepts, and Raven's coloured progressive matrices. To conclude, pictures at retrieval improve prospective memory performance compared to words as cues. This can be essential for the intellectual disability group likely due to limited episodic and working memory capacity and the ability to switch attention.