Ben 10: Alien Swarm follows teenage hero Ben Tennyson as he breaks ranks from the Plumbers (a secret organization that battles alien forces) to help Elena, a mysterious young woman, uncover an alien threat to our world. Joining him on his adventures are Gwen and Kevin, super-powered heroes in their own right, who must trust each others instincts to help save the day.

The movie begins with an extraterrestrial humanoid species wandering through space in search of a new world. Encountering an unknown planet which turns out to be Earth, their leader (Cyrillus) sends two manned probes to the surface to determine if it is suitable for colonisation.

During an archaeological expedition on Bouvetшya Island in the Antarctic ocean, a team of archaeologists and other scientists find themselves caught up in a battle between the two legends. Soon, the team realise that only one species can win.

In Gunnison County, a spacecraft crashes in the woods bringing a powerful hybrid Alien hosted inside the pilot Predator. The local Buddy Benson and his son Sam are hunting in the forest and witness the crash, but they are chased and killed by the Alien. Meanwhile another Predator lands on the spot seeking out the Alien and destroying the evidences of their presence on Earth. The dwellers of the town find themselves in the middle of a battlefield between the two deadly extraterrestrial creatures, and the small group of survivors splits the leadership between Sheriff Eddie Morales and the bad-boy Dallas Howard that have different opinions about the best means to escape from the beings.

When a mining ship lands on a planet to investigate upon a suspected SOS, the entire crew are unaware of the terror which they would unleash upon their ship. When a alien life-form attach's itself to the face of a crew member, the rest of the team act fast to try and separate the two organisms. Unbeknownst to everyone, this is the start of the terror which would affect every member of the seven person crew.

After escaping from the alien planet, the ship carrying Ellen Ripley crashes onto a remote and inhabited ore refinery. While living in the ore refinery until she is rescued by her employers, Ripley discovers the horrifying reason for her crash: An alien stowaway. As the alien matures and begins to kill off the inhabitants, Ripley is unaware that her true enemy is more than just the killer alien.

Crowds of blood thirsty monsters, crawling from every corner of the secret research base. Gloomy basements and modern labs, darkness changing into blazing bulbs. The only usual thing is: you’re in a bad place alone, and there’s no one to help you!