Junius Brutus and Sicinius Velutus are among the tribunes elected early in the play to represent the Roman citizens. Their main role is to safeguard the people's rights by keeping them updated on senate activities and gathering them to seek their opinions. As representatives of the populace, they are justified in viewing Coriolanus's disdain for the plebeians as a valid reason to oppose his bid for consul. They might genuinely believe, as Brutus states at II.iii.256-57, that the minor rebellion they are promoting will alleviate political tensions and prevent a larger civil conflict in the future. As politicians, they exhibit a clear grasp of effective campaigning. They are well-organized and ensure—through the aediles—that citizens turn out to vote.

However, Sicinius and Brutus significantly overreach their responsibilities. Most critics agree that they corrupt the tribune office. They seem more interested in preserving their own power than serving the public. Coriolanus is their adversary, just as he is the people's, and they are aware of this. If he were elected, their positions would be threatened, which appears to be their primary motivation. They understand that Coriolanus's arrogance is a political liability, and they skillfully manipulate him into revealing it in front of the populace. They seem envious of the enthusiastic reception he gets upon returning from Corioles, which may partly drive their actions to undermine him. They provoke him with words they know will anger him—such as "traitor"—and wait for the inevitable reaction.

They do not appear as astute in their interactions with Menenius, who makes a mockery of them without their noticing. During the peaceful period following Coriolanus's exile, they become complacent, noting that "the world goes well" and observing tradesmen happily "singing in their shops, and going about their functions friendly" (IV.vi.5, 8-9). The resurgence of hostilities by the Volscians, led by Coriolanus, catches them off guard, and initially, they refuse to believe it is possible. However, the people remember who orchestrated Coriolanus's banishment. In V.iv, Sicinius learns that the citizens have captured Brutus; moreover, they are dragging him "up and down" and threatening to kill him "by inches" (V.iv.37, 39) if the women's appeal to Coriolanus fails. Sicinius gratefully thanks the messenger who informs him that Volumnia has convinced her son not to attack Rome, which presumably also saves Brutus's life.