Prosody is an important feature in communication, and the way a speaker uses the various elements of prosody in public speaking may affect listeners’ perceptions and thus the speaker's credibility. This paper explores this topic in relation to speeches made in English by three politicians representing their countries’ 2020 Olympic bids at the 125th IOC (International Olympic Committee) Session in Argentina in September 2013. Of these, the speech given by the Mayor of Madrid, Ana Botella, received widespread critical attention due her style of delivery. As such, it illustrates the importance of prosody in public speaking. However, how prosody affects credibility remains unclear. The aim of this study is to analyze the influence of prosody on listeners’ perceptions of politicians’ credibility. We conducted prosody analysis and rhetorical analysis on the three-minute speeches given by the different candidates at the IOC Session. We also conducted a credibility test to assess the relationship between prosody and credibility. The results confirm that prosody influences speakers’ credibility, with the most credible and the best speaker being the politician who used the highest loudness, a moderate pitch level with a wide pitch range, and a faster speech rate with enough pauses of sufficient length. The study also showed that the less influential the prosody parameters were, the more credible the speaker was perceived to be.