A major dilemma for the nuclear non-proliferation regime is whether and how to engage the nuclear-armed states that are not in the Non-Proliferation Treaty (NPT) more effectively in the broader nuclear non-proliferation regime without weakening or discrediting the NPT. The Indo-U.S. Civilian Nuclear Agreement claims to bring India, as a “responsible” nuclear state, closer to the nuclear non-proliferation regime. It was criticized by the non-proliferation community, concerned that global non-proliferation norms would be undermined by India specially.This chapter employs a realist constructivist approach to understand how the U.S.-India nuclear agreement has affected the key norms of the global nuclear non-proliferation regime by deviating from the established expectations of the regime, and why the U.S. went to great efforts to sell the agreement as consistent with non-proliferation norms.