Conflict in Afghanistan, either Soviet invasion of Afghanistan or war on terror in post 9/11 period, has deep impact on Pak- US relations. In both the cases Pakistan got the status of the most important state strategically. It played important role as a front-line state to fight against the Soviet Union during Soviet attack of Afghanistan. As a result, America extended economic and military support to Pakistan. After the withdrawal of the Soviet Union from Afghanistan, American Foreign policy towards Pakistan was changed; it stopped all kind of economic and military support to Pakistan and imposed sanctions on it. Again, in post 9/11 attacks on American soil, America decided to attack Afghanistan and it needed Pakistan’s logistic support. Pakistan extended the required support and again became an important American ally in operation in Afghanistan. Thus, we may say, that conflict in Afghanistan has deep impact on Pak- US relations.