After finishing 22-33 a year ago, the Bulldogs (44-23-1) will go for their second national title 18 years after winning their first.
The Bulldogs beat Miami in their CWS opener and then Stanford on Monday. Their reward was supposed to be a three-day rest. But rain Thursday pushed the schedule back a day.
The Bulldogs didn't appear at all rusty against the Cardinal (41-24-2).
Peisel's second home run in three CWS games and 12th of the season put the Bulldogs up 9-3 in the fifth. Peisel finished 3-for-5, making him 7-for-14 in Omaha.
Poythress, who became the eighth player in CWS history to hit three doubles in a game, drove in four runs while going 4-for-5. Joey Lewis added three RBIs.
The Cardinal, down 10-4 with two outs in the bottom of the ninth, scored four runs against All-America closer Joshua Fields.
Pinch hitter Colin Walsh hit an RBI single and pinch hitter Ben Clowe followed with a three-run homer to left. Cord Phelps flew out to end the game.
Georgia jumped on Stanford ace Jeremy Bleich (3-3) for six runs on eight hits in 3 1-3 innings.
Poythress' double off the right-field wall and Lewis' two-run single gave the Bulldogs a 4-0 lead in the third. Poythress' two-run single in the fourth made it 6-1.
Phelps hit an RBI triple and scored on Dean Weaver's wild pitch as Stanford cut Georgia's lead to three runs in the bottom half.
But after Lyle Allen and Miles Starr singled leading off the fifth, Peisel sent Drew Storen's 1-1 pitch barely over the wall in right field to make it 9-3.
There were only two down notes for Georgia offensively. Matt Cerione, who came in batting a nation-leading .463 in the postseason, struck out all five times at bat, and Bryce Massanari had his 18-game hitting streak end.
Nathan Moreau, the Bulldogs' No. 3 starter who got the call instead of ace Trevor Holder, lasted 2 1-3 innings, giving up one run on two hits and three walks. He left with the bases loaded in favor of Weaver (6-1), who was touched for three runs on six hits the next 3 2-3 innings.
Alex McRee held Stanford scoreless on no hits in the seventh and eighth before Fields came on and struggled in the ninth.