Introduction: Multi-sensory storytelling (MSST) is a storytelling method designed for individuals with profound intellectual and multiple disabilities (PIMD). It is essential that listeners be alert during MSST, so that they become familiar with their personalised stories. Repetition and the presentation of stimuli are likely to affect the alertness of listeners during MSST. Previous studies have only examined the overall level of alertness during MSST. This study focuses on changes in alertness over time during storytelling. Method: In this study, 27 direct support people read an MSST book 20 times with a person with PIMD. The 1st, 5th, 10th and 20th storytelling sessions were recorded. The relation between alertness and the active presentation of stimuli is analyzed using a time-window sequential analysis. We examined changes in alertness levels by comparing the four different storytelling sessions. Results: Higher levels of active alertness were observed when stimuli were actively presented. Alertness was not constant within storytelling sessions, and was related to the presentation of stimuli. Actively presented stimuli were associated with larger fluctuations in alertness. Discussion: Storytellers should present stimuli actively and for longer periods, in order to increase the alertness of listeners during storytelling.