This is a list of notable events, premieres, releases, series cancellations and endings, and other business ventures for Nickelodeon in the year 2003.
Shows
Series premieres
- April 12 - All Grown Up! premieres as the Kids' Choice Awards leadout; the series would officially premiere in November.
- August 1 - My Life as a Teenage Robot
- September 13 - Romeo!
Season premieres
- February 3 - The Wild Thornberrys season 5 (final)
- May 30 - ChalkZone season 2
- August 9 - As Told by Ginger season 3 (final)
- August 30 - All That season 9
- September 19 - The Adventures of Jimmy Neutron: Boy Genius season 2
Specials
- The Adventures of Jimmy Neutron: Boy Genius: "The Eggpire Strikes Back"
- October - The Adventures of Jimmy Neutron: "Rescue Jet Fusion"
Movies
Theatrical
Made-for-TV
- Maniac Magee
- July 12 - The Fairly OddParents: Abra-Catastrophe!
Comics
- The Rugrats comic strip is cancelled
Video games
- November 3 - The Fairly OddParents: Breakin' Da Rules
- November 10 - SpongeBob SquarePants: Battle for Bikini Bottom
Albums
- February 4 - ChalkZone: In the Zone
Books
- Ding Dong
- Llama Drama
- The Science Project
- Sky Scare
- Token Wishes
- January 1
- Battle of the Band
- Chew on This!
- Genius 101 : Exploring My World
- Jimmy on Ice
- SpongeBob JokePants
- The Time Pincher
- A Valentine for Tommy
- February 1 - A Pickles Passover
- May 1
- Chasing Dad
- Rugrats Go Wild! (novelization)
- June 1
- Hands Off!
- The Amazing SpongeBobini
- July 1
- Goddard, Come Home!
- No More Mr. Smart Guy
- August 1 - Scrambled Planets!
- September 1
- The Big Halloween Scare
- Canine Catastrophe!
- New Student Starfish
- Rugrats' Favorite Funnies
- Scavenger Hunt (Rocket Power)
- Special Delivery! (SpongeBob SquarePants book)
- SpongeBob AirPants: The Lost Episode
- October 1
- The Big Sweep (Rocket Power Ready-To-Read)
- Christmas in the City
- The Runaway Turkey
- SpongeBob's Christmas Wish
- November 3
- Holly Jolly Jimmy
- December 23
Home video releases
- January 28
- Rugrats Mysteries (VHS and DVD)
- SpongeBob SquarePants: Bikini Bottom Bash (VHS)
- SpongeBob SquarePants: Deep Sea Sillies (VHS)
- SpongeBob SquarePants: Tales from the Deep (DVD)
- March 4
- SpongeBob SquarePants: Anchors Away (VHS)
- SpongeBob SquarePants: Lost at Sea (DVD)
- SpongeBob SquarePants: The Sponge Who Could Fly (VHS)
- April 1 - The Wild Thornberrys Movie (VHS and DVD)
- May 27
- The Adventures of Jimmy Neutron: Confusion Fusion (DVD)
- The Adventures of Jimmy Neutron: Time Warp (VHS)
- The Adventures of Jimmy Neutron: When Pants Attack (VHS)
- Harriet the Spy (DVD)
- Good Burger (DVD)
- July 15 - The Fairly OddParents: Abra-Catastrophe! (VHS and DVD)
- July 29
- SpongeBob SquarePants: Laugh Your Pants Off (VHS)
- SpongeBob SquarePants: Sponge-a-Rama (VHS)
- SpongeBob SquarePants: Tide and Seek (DVD)
- August 26
- All Grown Up: Growing Up Changes Everything (VHS and DVD)
- NickToons Halloween (DVD)
- September 30
- NickToons Christmas (DVD)
- SpongeBob SquarePants: Christmas (VHS and DVD)
- October 7 - The Adventures Of Jimmy Neutron: Sea Of Trouble (VHS and DVD)
- October 28 - SpongeBob SquarePants: The Complete 1st Season (DVD)
- December 16 - Rugrats Go Wild (VHS and DVD)