An unlockable character is a hidden character that must be unlocked by completing certain criteria before being able to play as them. Every game in the Mario Kart series besides the first three (Super Mario Kart, Mario Kart 64 and Mario Kart: Super Circuit) has unlockable characters, although Super Circuit features colored Yoshis (light blue, pink and yellow) that are exclusive to single-pak multiplayer mode.
Mario Kart: Double Dash!! has a total of 4 unlockable characters.
- Special Item: Random Item
Mario Kart DS has a total of 4 unlockable characters.
- Dry Bones - Receive a gold trophy in the 50cc Special Cup.
- Daisy - Receive a gold trophy in the 50cc Lightning Cup.
- Waluigi - Receive a gold trophy in the 100cc Lightning Cup.
- R.O.B. - Receive a gold trophy in the Mirror Mode Special Cup.
Mario Kart Wii has a total of 14 unlockable characters.
- Baby Daisy - Earn a star in every single 50cc Wii cup.
- Baby Luigi - Unlock eight expert staff ghosts in Time Trials.
- Birdo - Play 16 Time Trials or win 250 Wi-Fi races.
- Bowser Jr. - Earn a star in every single 100cc Retro cup.
- Daisy - Win the 150cc Special Cup.
- Diddy Kong - Win the 50cc Lightning Cup.
- Dry Bones - Win the 100cc Leaf Cup.
- Dry Bowser - Earn a star in every single 150cc Wii cup.
- Funky Kong - Unlock four expert staff ghosts in Time Trials.
- King Boo - Win the 50cc Star Cup.
- Mii (Outfit A) - Win the 100cc Special Cup.
- Mii (Outfit B) - Unlock all expert staff ghosts in Time Trials.
- Rosalina - Have a Super Mario Galaxy save file, and play 50 races. Alternatively, earn a star in all eight Mirror Mode cups.
- Toadette - Play Time Trials on all thirty-two courses or win 1000 Wi-Fi races.
Mario Kart 7 has a total of 9 unlockable characters.
- Daisy - Win the 150cc Mushroom Cup.
- Wario - Win the 150cc Flower Cup.
- Rosalina - Win the 150cc Star Cup.
- Metal Mario - Win the 150cc Special Cup.
- Shy Guy - Win the 150cc Shell Cup.
- Honey Queen - Win the 150cc Banana Cup.
- Wiggler - Win the 150cc Leaf Cup.
- Lakitu - Win the 150cc Lightning Cup.
- Mii - Win the Special Cup and Lightning Cup in any engine class.
Mario Kart 8 has a total of 14 unlockable characters. Some have no concrete unlock conditions and are unlocked after winning a random cup. However, the same cup will not unlock more than 1 character.
- Rosalina - Random
- Metal Mario - Random
- Lakitu - Random
- Toadette - Random
- Baby Rosalina - Random
- Pink Gold Peach - Random
- Iggy Koopa - Random
- Roy Koopa - Random
- Lemmy Koopa - Random
- Larry Koopa - Random
- Wendy O. Koopa - Random
- Ludwig von Koopa - Random
- Morton Koopa Jr. - Random
- Mii - Always the 8th unlock.
In Mario Kart 8 Deluxe, all of the characters previously unlockable in the original are available at the start. However, only one unlockable character exists.
- Mario Kart 7 is the only Mario Kart game where Wario is an unlockable character.
- Mario Kart: Double Dash!! is the only Mario Kart game where Toad is an unlockable character.