Casey Sander was born in Washington, D.C. His father was an Air Force lieutenant colonel. While attending Nathan Hale High School in Seattle, Washington, as sophomore, he played shortstop on the school's baseball team.
In his senior year, he was a 10th round draft pick for the California Angels and was accepted after graduating high school in 1973. Though he had turned down football scholarships from Washington and Washington State University, he had an unsuccessful season with the Angels and was eventually released. Sander and Richard Karn attended junior high school and later attended Roosevelt High School in Seattle together and played against each other on the football team.
After being released from the Angels and playing one season for the Seattle Rainiers, he accepted a football scholarship from University of Puget Sound. He considered becoming a sports broadcaster and took up an acting class in hopes it would help his performance. He participated in college plays including Waiting for Godot. After earning a teaching degree, he briefly taught at Curtis Senior High School in University Place, Washington. After quitting, he drove to Los Angeles and worked as a shipyard hand, log-cabin builder, bartender and car dealer to get by before getting an acting agent.
His first significant work was in print advertising including being the "Winston man" for Winston Cigarettes. Sander has a son, Max, and a daughter, Mimi.