"I have since viewed footage taken of the day in question, when I wasn't there, and it paints an entirely different picture," he said in a statement via a representative and posted on the novel's official Facebook page. "The written commentary accompanying the edited video mischaracterizes what happened."
On Wednesday, TMZ
published a video allegedly from the set of "A Dog's Purpose" showing a dog in apparent distress while filming a stunt in rushing water.
CNN was not been able to independently verify the video's authenticity.
The video's release led to calls for boycott from People for the Ethical Treatment of Animals and caused producer Amblin Entertainment and distributor Universal Pictures to cancel plans for the movie's upcoming Los Angeles premiere event.
American Humane, an organization that ensures the safety and well being of animals used in film and TV productions, also placed an on-set monitor on leave following the unauthorized release of the video.
Cameron said he found the video "to be shocking because when I was on set, the ethic of everyone was the safety and comfort of the dogs."
Cameron said the additional footage from earlier in the day in question shows Hercules, the dog in the video, "joyfully jumping in the pool."
"When he was asked to perform the stunt from the other side of the pool, which was not how he had been doing it all day, he balked," Cameron wrote. "The mistake was trying to dip the dog in the water to show him it was okay -- the water wasn't his issue, it was the location that was the issue, and the dog happily did the stunt when he was allowed to return to his original spot."
At one point in the video released by TMZ, Hercules' head appeared to go under water and led one unidentified person on set to hurriedly call for the director to stop filming.
Cameron admits he "didn't like it when Hercules' head briefly went under water," but "there was a scuba diver and a trainer in the pool to protect him."
"[Hercules] loves the water, wasn't in danger, and wasn't upset," Cameron said.
He added: "On a movie where the mantra was the safety and comfort of the dogs, mistakes were made, and everything needs to be done to make sure those errors are not repeated. But the reason American Humane certifies that no animals were harmed during the making of the film is that no animals were harmed during the making of the film."
Amblin and Universal on Thursday had said their own "in-depth" review of the edited footage was taking place, but that they "continue to support this film, are incredibly proud of it."
"While we are all disheartened by the appearance of an animal in distress, everyone has assured us that Hercules the German Shepherd was not harmed throughout the filmmaking," the companies said.
"A Dog's Purpose," based on the book by Cameron, follows the story of a dog named Bailey (Josh Gad) over five decades as he experiences multiple owners and forms and "finds the meaning of his own existence" in the process, according to press materials.
Cameron, who is also co-wrote the film, questioned the timing of the video's release.
"If the people who shot and edited the video thought something was wrong, why did they wait fifteen months to do anything about it, instead of immediately going to the authorities?" his statement said.
He added: "I celebrate animal rescue and am proud of the values that show up in 'A Dog's Purpose.'"
The movie is due in theaters January 27.
CNN's David Daniel contributed to this story.