He led East Anchorage to the 1994 Alaskan State Championship and he played in the prestigious McDonald's All-American Game, where he won the 3-point shooting contest. He was also the recipient of the Dial Award, given to the nation's top male and female student-athlete. Langdon's win marked the second consecutive year a basketball player was so honored, as Jacque Vaughn had won the previous year.
After high school, Langdon moved on to play for the highly regarded Duke University basketball team, where he set the school record for most career 3-point field goals made (which was later broken by J. J. Redick in 2006) earning him the nickname "The Alaskan Assassin". After his Freshman year at Duke he twice appeared on the popular Anchorage, AK TV sports talk show, Sports Talk Alaska. Langdon was the only guest to ever appear on the show twice.
In the 1999 NCAA Men's Division I Basketball Tournament championship game, with Duke down 1 point to the UConn Huskies, with 5.4 seconds to go Langdon attempted to drive the ball into the lane and committed a traveling violation that turned the ball over to UConn. Analysts, as well as Langdon himself, credited the defense of Ricky Moore, who was considered the top defensive player in the tournament, for forcing the travel. A few also questioned why he had attempted to play Moore one-on-one, and had not instead passed the ball to guard William Avery. When Khalid El-Amin subsequently made two foul shots Langdon received the in-bounds pass and attempted to take a 3-point shot to tie the game, but tripped and lost control of the ball as time expired.