This paper studies the impact of domestic politics upon Indonesia's foreign policy-making. Serving as a non-permanent member of the United Nations Security Counil from 2007 to 2008, Indonesia voted on two key resolutions concerning the Iranian nuclear issue. While approving international sanctions against Iran under UNSC Resolution No. 1747, the Indonesian government preferred to abstain from voting on Resolution No. 1803. This paper argues the country's changing response to the Iranian nuclear issue was a consequence of domestic opposition. The case study specially identifies the interplay between majority Moslem population, religious mass organisations and political parties as key factors which weigh upon the "strategic calculus" behind Indonesia's foreign policy formulation. The paper will conclude while the executive still drives the country's foreign policy, the parliament and social-political groups have new powers to cajole and criticise the government into reversing or softening an established policy.