Learner engagement has been considered one of the keys that can lead learners to successful learning in a multimedia learning environment such as digital game-based learning. Regarding this point, game-based learning advocates (e.g., Gee, 2003; Prensky, 2001) have asserted that digital games have great potential to engage learners. Nonetheless, there have been only a small number of empirical research studies of players' engagement, and there is little consensus on which elements of digital games critically engage people in play (Garris, Ahlers, & Driskell, 2002). Furthermore, despite the possibility that sensory stimuli can be factors influencing digital game players' engagement, there have been very few attempts to examine empirically the relationship between engagement and sensory stimuli. This study examined the effects of game characters' voice-over in digital games on players' engagement, by using a short digital role-playing game modified from "Neverwinter Nights 2". A randomized control-group post-test only design was used to collect data from 74 participants (22 female, 52 male); engagement was measured by a modification of the Game Engagement Questionnaire (Brockmyer et al., 2009). Data analysis revealed that the GEQ mean scores of the participants who played the game with voice-over was much higher than that of the participants who played without voice-over. The difference of the mean scores between the two groups was statistically significant ( "t" = 2.45, "df" = 72 "p" = 0.02), and the effect size, Cohen's d, was 0.58 (moderately significant). The results of this study will guide educational practitioners to the identification of more effective ways of adopting, developing, and modifying digital games for educational purposes, as well as furthering the research and guiding the practice in instructional multimedia design and development. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]