This pilot study explored the instructional value and potential of a computer-mediated shadowing activity for improving English as a Second Language (ESL) learners' speech intelligibility. Prospective International Teaching Assistants (ITAs), who were enrolled in an ESL classroom communication class at a large public university, completed a computer-mediated shadowing activity using two web resources, Go Animate and TED talks. Then, these adult ESL participants were surveyed on their perceptions of the efficacy of this shadowing activity for improving their pronunciation, intonation, rhythm, and fluency. In addition, participants' speech samples recorded during the shadowing activity were independently assessed by certified ESL speaking exam raters. The evaluation results, including holistic proficiency scores and rater comments, were analyzed in terms of pronunciation, prosodic control, and overall intelligibility of the speech samples. Although the study is inconclusive, findings from this case study suggest that the computer-mediated shadowing activity may well be an effective means to raise ESL learners' awareness of the problems in their prosodic control and help them to improve their speech intelligibility.