As the wind picked up at the start of Sunday's game, the "Call Me Maybe" singer held on to the baseball too long, causing it to land with a thud just feet from where she was standing on the pitcher's mound.
The ball then slowly rolled across the ground toward the first base line, instead of where it was supposed to go -- to the batter standing at home plate.
Jepsen reacted to the bad pitch by laughing and covering her face.
FOX Sports posted a video clip of the moment on YouTube under the headline, "Carly Rae Jepsen Throws Terrible First Pitch."
Jepsen was chosen to throw out the opening pitch because she was scheduled to perform as part of the Rays Summer Concert Series after the game, Zap2it.com said.