The 27-year-old suffered the injury in a speed drill at training on Monday and had surgery later that day.
"At exploratory surgery, the achilles tendon was found to be completely ruptured and has been surgically repaired," club doctor Andrew Potter said.
"The recovery time for the injury will be at least three months."
List development and strategy general manager David Noble said the injury was an unfortunate setback for van Berlo who had been enjoying a good pre-season.
"But he's an extremely professional athlete and we know he'll leave no stone unturned in his recovery," Noble said.
"We'll support Nathan and work with him to ensure he's back on the park as soon as possible."
Van Berlo has played 182 games in nine seasons for Adelaide and has been captain since 2011.