Thieves used power tools to cut off the heads of three velociraptors at the National Dinosaur Museum in Nicholls on Saturday night.
CCTV footage showed the dinonappers arrive in a 4x4 dual cab ute shortly before 11pm before climbing a four foot fence to get to the dromaeosaurids.
The dino museum's supervisor Mitchell Seymour said it wasn't the first time vandals had targeted their dinosaurs.
"It's just thoughtless and senseless opportunism actually," Mr Seymour said.
"There's not much we can do: we have the gates that are locked, we have everything chained down, we have security cameras."
"We kind of have to rely on people not being awful."
In March 2013, thieves stole a Utahraptor statue as part of a birthday prank.
A three day hunt ended when police received a tipoff it was being held at 20-year-old man's home in Page.
Later that year, vandals caused $2500 in damage when they smashed apart three statues.
Arms had been ripped off two velociraptor statues while a Parasaurolophus had been pushed onto rocks.
In 2015, thieves stole a $1000 Protoceratops statue from a promotional display for Jurassic World from the Hoyts in Belconnen.
This time police said the velociraptors appeared to have been decapitated with angle grinders and a hacksaw.
Mr Seymour said he believed the raptor heads would be kept by the thieves.
"I mean it's going straight to the pool room, right? They've just got them to have them," Mr Seymour said.
Staff at the museum only noticed the damage after they opened on Sunday morning when patrons asked what had happened to raptors.
"We opened up to the public and we had some people coming up, saying what's happening with the dinosaurs up the front," Mr Seymour said.
He said kids had been asking their parents, "Mum and dad, what's happened to the dinosaurs?".
"They're down in our workshop at the moment," Mr Seymour said.
Police found the damaged raptors on Sunday, August 6 and appealed for witnesses to come forward.
Anyone with information or saw suspicious around the National Dinosaur Museum on Saturday night should contact Crime Stoppers on 1800 333 000 or via the ACT Crime Stoppers website.