This study aims for a rhetorical analysis of an old poetic discourse using modern approaches, which can be found in the field of argumentative theories, poetic pragmatics, and discourse analysis. The study also makes use of the knowledge heritage which old Arabic rhetoric has provided, acting as a discourse analysis theory. The study addresses ethos in the poetic discourse of Antarah ibn Shaddad from the standpoint that the discourse is defending the self which suffers social injustice, and also acts as a dialogue with the other party, who undermines that self because of slavery or skin colour. Ethos has been one of the most important defensive strategies used for the rebuttal of negative self-image, and replacing it with a positive one. To build an ethos, The poetic discourse has relied on some methods that provided it with strength and credibility, such as poetic narration of the speaker's characteristics and actions, and employing rhetorical concepts to leave an impact on the recipient's mind and emotions. Keywords: Arabic rhetoric - Poetic discourse - Communication - Argumentation - Pragmatics - Antarah ibn Shaddad.