Ben 10: Alien Force is set five years after the original series. The storyline is notable for having matured the character and taking a darker tone, with more complex plots and more characters dying. This change received mixed reactions from the fans, and caused a division amongst them.
Five years after the events of the original series, 15-year old Ben Tennyson has returned to a normal, everyday life. His adventures all done, Ben has taken off the Omnitrix and has grown from a young boy into a confident teenager; however, the mysterious disappearance of Grandpa Max forces Ben to wear the Omnitrix again, as well as forcing him, his cousin Gwen, and his old enemy Kevin to search and locate Grandpa Max. At the same time, they must enlist the help of the Plumbers' kids (children or grandchildren of retired Plumbers which are commonly half human and half alien) and repel attacks from a new enemy, the Highbreed. In the third and final season, Vilgax returns as the main antagonist forcing Ben, Gwen, and Kevin to tackle bigger problems and find out more secrets about the Omnitrix.
- Ben Tennyson
- Gwen Tennyson
- Kevin E. Levin
- Julie Yamamoto
- Max Tennyson
- Professor Paradox
- Carl Tennyson
- Sandra Tennyson
- Cooper Daniels
- Manny Armstrong
- Helen Wheels
- Alan Albright
- Highbreed (neutral)
- Ragnarok (presumed deceased)
- Techadon Robots
- The Forever Knights
- Zs'Skayr (defeated)
- Alien X
- Big Chill
- Echo Echo
- Nanomech (only in Alien Swarm)
- Way Big
- Heastblast (Hologram only)
- List of Ben 10: Alien Force episodes.
- Ben 10: Alien Force The Video Game
- Ben 10 Alien Force: Vilgax Attacks
- Ben 10 Alien Force: The Rise of Hex
- This series feature the least amount of additional aliens with only 2 additionals (Nanomech doesn't count because he was never unlocked and used in this series).
- While most of the episodes took place during daytime in the original series, many of the Alien Force episodes took place at night.
- Season 1 and 2 were supposed to be one season, but Cartoon Network cut it in half without the writers' approval.
- It originally went with the working title, Ben 10: Hero Generation.
- From this series onward, Dee Bradley Baker provides the voices of all Ben's alien forms (with the exception of Alien X, Ghostfreak and Rath.
- There are no season 3 Ben 10 Alien Force toys eg. Mutated Kevin and Charmcaster (though Albedo (with red ultimatrix), Vilgax, Diamondhead, Way Big, Lodestar and Rath have UA toys).