It's the year 2149, and Earth is at the verge of environmental ruin. People must wear special masks called rebreathers in order to survive outside, and families are required by law to bear only two children. However, hope comes in the form of a fracture in reality. The crack is a portal to the distant past, and humanity has already begun sending people through the portal to a new human colony called Terra Nova.
Jim Shannon arrives home with a precious gift, a real orange. He doesn't give an explanation of where the rare fruit came from, but he offers it to his children. Son Josh starts peeling it for his younger sister, Zoe. Things take a turn for the worse when Population Control pays a visit. The family hides Zoe, but she's found anyway. Jim takes blame for the violation, assaults the Population Control officers, and is sentenced to prison for the crime.
Two years after the incident, Jim's wife Elisabeth pays off a guard to get into the prison to deliver two pieces of good news. She has been recruited to Terra Nova, which means their family has a chance for a new beginning. The second piece of good news is a rebreather for Jim, and the device also contains a tiny laser, which Jim uses to escape.
Elisabeth, Josh, and his other sister Maddy are preparing to go to Terra Nova on the Tenth Pilgrimage. Josh is leaving behind a girlfriend. Jim joins his family after strong-arming his way to the portal facility. He carries with him a backpack containing some precious cargo. He fights his way through the portal, attacking guards, and rushing through the gate into the past.
The guards at Terra Nova surround Jim after noticing he brought a gun through the gate, and they're about to slash open his pack. Jim and Elisabeth panic and hurriedly open the backpack, that has their daughter Zoe hiding inside. The Shannons join the rest of the colonists and are welcomed by Terra Nova's leader, Commander Nathaniel Taylor.
After the welcome speech, Jim and Elisabeth are brought before Taylor. Jim tries to take on all the blame, but Taylor is certain the man couldn't have done it alone. Taylor's aware that Jim escaped prison, but he doesn't care about the laws from another time. Taylor just wants people who are of use to the colony. Since Elisabeth was recruited, the colony needs her, so Taylor assigns Jim to agricultural duty.
The Shannons are shown their new home, which is enormous compared to the cramped apartment they had shared in 2149. Zoe is upset because there isn't a separate room for her, but Maddy agrees to share her room with her sister. Zoe is excited when she encounters dinosaurs for the first time, as she marvels at a group of sauropods that are busy chewing on the leaves right outside the fence near the Shannons' new home.
The children are sent off to orientation and Maddy is excited to spot the probe that scientists from her time had sent into the past. She tells a disinterested Josh that the scientists were unable to find the beacon's signal, which indicated the portal opened into an entirely separate time stream than the future from whence they had come, which means Terra Nova can avoid influencing Earth's future.
Jim is assigned to do some weeding, which means hacking down a gnarled mass of vines from a section of fence. One of Elisabeth's patients suddenly turns on her, attacks her, and steals supplies and a gun from a guard. Jim's cop instincts kick in and he notices the man acting suspiciously. He captures him, which impresses Taylor.
Josh blows off orientation and meets a girl named Skye, who offers to show him around. She and her friends take Josh outside the gates without permission. Skye and Josh end up near a waterfall, where she shows him some mysterious markings carved into the rocks. Skye says that Taylor doesn't want people to know that these engravings exist.
Taylor takes Jim aside and explains that there is a splinter group of colonists who broke away from the main group called Sixers because they all came to Terra Nova on the Sixth Pilgrimage. The Sixers brought weapons with them, but their motives are unclear. The man who attacked Elisabeth and Jim had captured is a Sixer.
Sixer vehicles are spotted outside the perimeter of the colony. Apparently, they want their captured comrade back. Taylor and Jim race after them in their own vehicle, but things grow complicated when a few carnotauri begin chasing all of them. The chase ends with Sixer vehicles barreling through the gates of Terra Nova. A woman named Mira climbs out of the vehicle, and notices a new face: Jim. With a sardonic smile on her face, she welcomes him to paradise.