The research examined the effect of an intervention program employing 3D immersive virtual reality (IVR), which focused on the perception of sequential time, on the mediation level and behavioural aspects of children with intellectual disability (ID). The intervention is based on the mediated learning experience (MLE) theory, which refers the quality of interaction between a mediator and learner. The intervention program, which included three mediation levels--full, partial and no mediation--was applied in individual-based direct instruction: the emotional, cognitive and behavioural dimensions of the participants' behaviours. Eighty-seven participants with mild to moderate ID between the ages of nine and 21 participated in the study. They were divided into two experimental groups, one of which was exposed to sequential time scenarios in 3D IVR, while the other experienced the same scenarios via a series of 2D pictorial episodes. Our findings indicate that the 3D IVR group required less mediation as compared with the 2D pictorial group. In addition, the participants with moderate ID needed more mediation than did those with mild ID. In the behavioural dimension, it was found that in most of the scenarios there was a distinct advantage for the participants in the 3D IVR group--they were more focused on the assignment, more immersed physically in the virtual worlds and were less frantic and stressed. (Contains 6 tables and 2 figures.)