The new law was signed last weekend by the midwestern state's Republican governor Scott Walker, and goes into effect almost two weeks after a mass shooting at a Sunday church service in Texas renewed debate over gun violence.
Dozens of states do not bar young children from hunting with adult supervision. But many limit hunting of bigger animals such as deer and bear to older children, roughly 12 years or above depending on the jurisdiction.
The Wisconsin law eliminates a previous age restriction of 10, allowing any child to carry a hunting weapon if accompanied by a trained adult.
The youngsters will be able to use their own weapons, not just share one with the adult as many states require, and they will also be able to go after big game.
The National Rifle Association (NRA) and the Wisconsin Bear Hunters' Association were among the law's proponents, arguing it will allow parents to pass on hunting traditions to future generations.
The law becomes effective at the beginning of the state's annual nine-day period of deer hunting by gun in its millions of acres (hectares) of woods, where white-tailed deer, bear, wild turkey and other animals are hunted.
"I learned how to safely handle the gun I had in my hands by watching the people who mentored me," he said, adding that 34 other states permit "mentored hunting" under the age of 10.
The law's opponents argued children under 10 were simply too young to carry dangerous weapons, even if an adult accompanied them.
"If you sit in a booster seat on the way to the hunt, you probably shouldn't be handed a gun when you get there," said gun control advocacy group Wisconsin Anti-Violence Effort.
The new law comes after two mass shootings in the last two months that shocked many in the US, where gun violence claims the lives of an average of almost 34,000 people a year, according to the prevention group Brady Campaign.
A gunman killed more than two dozen worshippers at a Texas church service on November 5, including eight children. Five weeks earlier, the nation's worst gun massacre in recent memory claimed the lives of 58 people at an outdoor Las Vegas concert.