The objective of this article is to compare ethical accounts of responsibility of Karl Barth and Mou Zongsan with a particular concern of how they relate ethical beliefs to political practice. Specifically, Barth believes that responsibility captures our free, grateful and obedient response to the Word of God in the covenantal relationship. Mou teaches that the responsibility of moral subjects implies our affirmative response to the innate knowledge of good and opposition to our evil. When applying to social and political issues, both of them resisted all forms of hegemony and shared a fundamental concern that any humane political system cannot sustain without a robust understanding of responsibility. This article suggests that the connection between their concepts of responsibility and social engagement is worth exploring, and their ethics of responsibility is still inspiring for reflection on similar issues in the context of contemporary China.