| Real Name | Character Name | Notes |
| Molly Ringwald | Samantha Baker | |
| Justin Henry | Mike Baker | Sam's little brother |
| Michael Schoeffling | Jake Ryan | The senior guy Sam is in love with. He's dating Carolyn. |
| Haviland Morris | Caroline | She's dating Jake Ryan. |
| Gedde Watanabe | Long Duk Dong | Foreign exchange student staying with Grandma and Grandpa Baker |
| Anthony Michael Hall | Ted/Farmer Ted/The Geek | King of the dipshits. He's got the hots for Sam. |
| Paul Dooley | Jim Baker | Sam's father. |
| Carlin Glynn | Brenda Baker | Sam's mother |
| Blanche Baker | Ginny Baker | Sam's older sister who's getting married. |
| Edward Andrews | Howard Baker | Sam's grandfather on her father's side. |
| Billie Bird | Dorothy Baker | Sam's grandmother on her father's side. |
| Carole Cook | Helen | Sam's grandmother on her mother's side. (The smoker) |
| Max Showalter | Fred | Sam's grandfather on her mom's side. (The joker) |
| Liane Alexandra Curtis | Randy | Sam's best friend |
| John Cusack | Bryce | He's one of two main geeks which hangs with Ted. |
| Darren Harris | Cliff | He's one of two main geeks which hangs with Ted. |
| Deborah Pollack | Lumberjack | Long's new American style girlfriend. |
| Ross Berkson | Ray Gun Geek #1 | |
| Jonathan Chapin | Jimmy Montrose | |
| Joan Cusack | Girl with MS brace | |
| Brian Doyle-Murray | Reverend | Performs the wedding. |
| Bekka Eaton | Female DJ | |
| Pamela Elser | Shower Double (Caroline) | |
| Steven Farber | Ray Gun Geek #2 | |
| Jami Gertz | Robin | One of Caroline's friends. Also starred in SQUARE PEGS (TV). |
| Frank Howard | Freshman | Randy's little brother. Paid $1 to see Sam's underpants. |
| Cinnamon Idles | Sara Baker | Sam's little sister. Has a Charlie's Angles lunchbox. |
| John Kapelos | Rudy | Ginny's fiancee/oily bo-hunk |
| Marge Kotlisky | Irene | |
| Tony Longo | Bock | |
| Steve Monarque | Jock | |
| Bill Orsi | Bruno | |
| Beth Ringwald | Patty Baker | No one knows where she is in the film. She is NOT Sam's little sister. |
| Zelda Rubinstein | Organist | The organist at the wedding. She was also in Poltergeist. |
| Dennis Vero | Bus Driver | Drove Sam's school bus |
| Elaine Wilkes | Tracey | She cut Caroline's (Haviland Morris) hair |
| Stephan Meyers | Geek at Dance (uncredited) | which one? |
