Rachel McAdams - Regina George

Lizzy Caplan - Janis Ian

Lacey Chabert - Gretchen Wieners

Amanda Seyfried - Karen Smith

Tina Fey - Ms. Norbury

Daniel Franzese - Damian

Jonathan Bennett - Aaron Samuels

Tim Meadows - Mr. Duvall

Amy Poehler - Mrs. George

Ana Gasteyer - Cady's mom

Neil Flynn - Cady's Dad

Rajiv Surendra - Kevin Gnapoor

Elana Shilling - Spelling Girl

Graham Kartna - Homeschooled Boy

Ely Henry - Homeschooled Boy

David Aherne - Homeschooled Boy

Ayo Agbonkpolo - African Warrior

Molly Shanahan - Kristen Hadley

Jeff Moser - "Farting" Guy

Miranda Edwards - Michigan Girl

Les Porter - Chemistry Teacher

Daniel DeSanto - Jason

Diego Klattenhoff - Shane Oman

Dwayne Hill - Coach Carr

Alexandra Stapley - Taylor Wedell

Nicole Crimi - Kylie George

Julia Chantrey - Amber D'Alessio

Stefanie Drummond - Bethany Byrd

Jo Chim - Salesperson

Jill Morrison - Crying Girl

Clare Preuss - Caroline Krafft

Krysta Carter - Wannabe (uncredited)

Dan Willmott - Mr. George

Sharron Matthews - Joan the Secretary

Ky Pham - Trang Pak

Olympia Lukis - Jessica Lopez

Jan Caruana - Emma Gerber

Erin Norah Thompson - Dawn Schweitzer

Danielle Nguyen - Sun Jin Dinh

David Reale - Glenn Coco

Wai Choy - Tim Pak

Alisha Morrison - Lea Edwards

Jonathan Malen - Kristen's boyfriend

Laura de Carteret - Taylor's mom

Chris Anton - Huge Guy

Jacky Chamberlain - Giselle Sgro

Kristen Bone - Short Girl