Prior to his election to the U.S. Senate, Sullivan served as Alaska's Attorney General and Commissioner of the Alaska Department of Natural Resources. As Alaska's Attorney General, Sullivan's number one priority was protecting Alaskans, their physical safety, financial well-being, and individual rights - particularly Alaska's most vulnerable. During his tenure he spearheaded a comprehensive statewide strategy - the "Choose Respect" campaign - to combat Alaska's high rates of domestic violence and sexual assault. Under Sullivan's leadership, the Department of Law also undertook an aggressive strategy of initiating and intervening in litigation aimed at halting federal government overreach into the lives of Alaskans and their economy.

As Commissioner of the Alaska Department of Natural Resources, Sullivan managed one of the largest portfolios of oil, gas, minerals, renewable energy, timber, land, and water in the world. Working closely with Alaska's Governor and state legislature, Sullivan developed numerous strategies that spurred responsible resource development, energy security, and a dramatic increase in good-paying jobs across a number of critical sectors in the Alaska economy. He also developed a comprehensive plan to streamline and reform the state's regulatory and permitting system.

Sullivan is one of a select number of Alaskan attorneys who has held judicial clerkships on both the highest federal and state courts in Alaska. He served as a judicial law clerk for Judge Andrew Kleinfeld of the United States Court of Appeals for the Ninth Circuit in Fairbanks, Alaska and for Chief Justice Warren Matthews of the Alaska Supreme Court in Anchorage, Alaska. Sullivan also served as a judicial law clerk/intern for Judge James L. Buckley on the United States Court of Appeals for the District of Columbia Circuit.

Sullivan has a distinguished record of military and national security service. He is currently a Colonel in the U.S. Marine Corps Reserve. Since 1993, Sullivan has served in a variety of command and staff billets on active duty and in the reserves, including- TRAP Force Commander and 81mm mortar Platoon Commander, 31st Marine Expeditionary Unit (Special Operations Capable); Weapons Company Executive Officer, Second Battalion, Fifth Marines; Commanding Officer, Delta Company, Anti-Terrorism Battalion; Executive Officer, Echo Company, Fourth Reconnaissance Battalion; and Commanding Officer, 6thAir Naval Gunfire Liaison Company (ANGLICO). In 2004, Sullivan was recalled to active duty for a year and a half to serve as a staff officer to the Commander of U.S. Central Command, General John Abizaid, spending substantial time deployed in the Middle East, the Horn of Africa, and Central Asia. In July 2013, Sullivan was recalled to active duty to serve with a Joint Task Force in Afghanistan focusing on dismantling terrorist networks and criminalizing the Taliban insurgency.

Sullivan served in the Administration of President George W. Bush as the U.S. Assistant Secretary of State for Economic, Energy, and Business under Secretary of State Condoleezza Rice. He focused on fighting terrorist financing, and implementing policies relating to international energy, economic, trade, finance, transportation, telecommunications, and Arctic issues. Sullivan also served as a Director in the International Economics Directorate of the National Security Council staff at the White House.

Sullivan earned a B.A. in Economics from Harvard University in 1987 and a joint law and Masters of Science in Foreign Service from Georgetown University in 1993. Dan and his wife Julie Fate Sullivan were married in 1994 in Julie's hometown of Fairbanks, Alaska. They have three daughters.