The kids battle with the lizard after it wrapped itself around their pet's lower body and rear legs with sticks and a metal table leg.
However, the clip shows the snake clenching its jaws and tightening its vice-like grasp on the dog.
Eventually, the boys untangle the giant serpent from the free-running dog.
At the end of the 21-second clip, the older boy lifts the writhing snake by its head.
The location and date of the dramatic footage are unknown, but it has been widely circulated online this week.
Many people praised the boys' bravery.
"The poor dog - he was absolutely terrified," one social media user commented. "Well done, children!"
"Well done to the people who saved the lovely dog!" said a third. "I hope he's doing well."
Some even demanded that the boys be awarded for their bravery.
"Wonderful video. "Those kids should be recognised for their bravery and love for their dog," a Facebook user stated.
Boa constrictors, which are common in North and South America, can grow to be up to 13ft long.
They surprise their prey, which includes huge birds, bats, lizards, and rodents.