A phonological similarity effect (PSE) in adolescents with an intellectual disability (ID) has previously been shown with auditory stimuli, but studies using visual stimuli are scarce. In the case of visually presented items, PSE requires verbal recoding before it appears. Using visual items, we trained 15 participants with ID to use rehearsal strategies. Another group of 13 participants took part in nonstrategic training. In both groups, PSE was tested before and after training. Participants in the strategy-training group, who showed no PSE at pretest, began to show such an effect during the training stage and maintained it until posttest as was observed through microgenetic analysis. Participants with ID showing no PSE with visual material can thus be trained to show this effect through extensive use of cumulative rehearsal. Such training would lead them to recode items verbally, which in turn would make phonological similarities more salient and lead to a PSE.