The loss ends a recordbreaking season for the Golden Eagles, which featured Burroughs High graduates Kyle Williams and Mike Diaz.
Cal State L.A. was making its first appearance in the NCAA Division II semifinals. It was the program's second-ever trip to a national semifinal, as the Golden Eagles advanced to the final four as a Division I team in 1977.
The Golden Eagles (45-17-1) also set a new program record for most wins in a season and claimed the NCAA West Region championship.
Diaz started the game as designated hitter and went one for two with a run batted in and a walk. He delivered a run-scoring single in the fifth inning, as Cal State L.A. later tied the score at 4 after falling behind, 4-0.
In the fourth-inning rally, Jeff Carroll had a two-run single and Matt Winkelman also drove in a run.
Williams, who started at second base, didn't have a hit in three at-bats, but made some fine plays in the field.
After tying the score, the Golden Eagles made some outstanding defensive plays in the sixth inning to keep the Cougars (51-18) from taking the lead.
However, Columbus State — the 2002 national champion — pushed across five runs in the last three innings.
Catcher Trent Bianco (four for five with two RBI) broke the tie with a one-out single to right-center field in the seventh.
The team added two runs each in the eighth and ninth innings and outhit the Golden Eagles, 18-6.
No Cal State L.A. player had more than one hit.
Cal State L.A.'s Isaac Morales pitched the first three innings and gave up a two-run first-inning home run to Brad Linton, and nothing else. He gave up six hits and walked a batter.
Columbus State jumped out to a 4-0 lead with Linton's two-run home run in the first and a sacrifice fly by David Brown and a run-scoring single by Trent Bianco in the fifth.
The loss ends the careers of Williams and Diaz, who finish up their senior seasons with the Golden Eagles. Williams was a four-year player in the program and Diaz joined the squad prior to the season.
Both were all-league first-team players at Burroughs, graduating in 2003.