Smith graduated from Fordham University in 1987 with a bachelor's degree. He completed a law degree at the University of Washington in 1990. He worked his way through college via employment on a loading dock at a trucking company. After college, Smith spent two years as a private practice attorney with Cromwell, Mendozza, and Belur. From 1993 to 1995, he worked for the city of Seattle as a procescutor. In 1996, he worked temporarily as a pro tem judge.
Smith is a member of the House Armed Services Committee and the House International Relations Committee. He has been a leader in moderate, "New Democrat" organizations. He serves as the chair of the political action committee of the New Democrat Coalition.
On October 10, 2002, Adam Smith was among the 81 Democratic members of the House voting in favor of authorizing the invasion of Iraq.
In 2006, Smith won his sixth term in Congress. His opponent was Republican Steve Cofchin. Smith won 65.7% of the vote to Cofchin's 34.3%. 
In April 2007, Smith threw his support behind Senator Barack Obama for the 2008 Presidential Election.
He has also appeared on Hardball with Chris Matthews speaking for Obama.
Smith voted against the Protect America Act of 2007, which has been criticized for violating American citizen's civil liberties by allowing for wiretapping without issued warrants.