As of Thursday, using it while driving is illegal.
The new law bars anyone operating a motor vehicle under an instruction permit or a probationary license from using a cellphone or other wireless communications device except to report an emergency.
First-time violators would face penalties ranging from $20 to $40.
Wisconsin State Patrol Maj. Sandra Huxtable said the hope is the new law will deter teenagers and other inexperienced drivers from talking on their phones while driving, which can be a dangerous distraction.
The law primarily affects young drivers, but those on probationary licenses can be older and include people who were licensed in other countries.
State law already prohibits drivers of any age from texting while behind the wheel.