Children with mental retardation have pronounced difficulties in using cognitive strategies and comprehending abstract concepts--among them, the concept of sequential time (Van-Handel, Swaab, De-Vries, & Jongmans, 2007). The perception of sequential time is generally tested by using scenarios presenting a continuum of actions. The goal of this study was to test whether the perception of sequential time among teenagers with mental retardation would improve, by using an intervention program employing 3D Immersive Virtual Reality (IVR). Eighty-seven teenagers with mild to moderate mental retardation, between the ages of 9 to 21, participated in the study. They were divided into three groups: a) an experimental group, who experienced sequential time scenarios in 3D IVR; b) one control group, who experienced the same scenarios via a series of two-dimensional (2D) pictorial episodes; and c) a second control group, who underwent no program of intervention. Our findings indicate that the participants who used the IVR program improved their time perception more than did the other members of the two control groups. In addition, the results reveal that the achievement required less moderation than executed with the control groups. Similarly, the results indicate that teens with mild retardation achieved a higher degree of sequential time perception than did those with moderate retardation. (Contains 5 tables and 3 figures.)