Pierce City held on despite being outhit six to two, and striking out 13 times against Lamar pitcher Emmie Roberson.
"The game was very tense," said Pierce City coach Kasy Gunnels. "We didn't hit well, but we scored one run and tonight that was enough."
The Lady Eagles plated the game's only run in the top of the third inning. Brooke Ridenour walked and stole second and scored on an error on a ball Monica Sexton hit to centerfield.
Lamar's Taylor Hardman tripled in the fifth inning, but Hardman was thrown out at home on a grounder hit to the Lady Eagles' Faith Strong.
McKenzie Moreland got the win for Pierce City, striking out five and walking none in the shutout effort.
Robertson struck out 13 and allowed just two hits, and walked one.
The Lady Eagles will travel to Pleasant Hope on Saturday, Oct. 13. The Lady Pirates, last year's state runner-up, topped Iberia 11-0 on Oct. 10. First pitch is set for noon.