This study explores Iranian influence in Afghanistan and the implications for the United States after the departure of most American forces from Afghanistan. Iran has substantial economic, political, cultural, and religious leverage in Afghanistan. Kabul faces an obdurate insurgency that is likely to exploit the U.S. and international drawdown. The Afghan government will also face many economic difficulties in future years, and Afghanistan is highly dependent on international economic aid. Additionally, the biggest problem facing Afghanistan may be political corruption. Iranian influence in Afghanistan following the drawdown of international forces need not necessarily be a cause of concern for the United States though. Although Tehran will use its cultural, political, and economic sway in an attempt to shape a post-2016 Afghanistan, Iran and the United States share core interests there: to prevent the country from again becoming dominated by the Taliban and a safe haven for al Qaeda.