The new law will take effect July 1.
It will require riders and passengers under age 16 who ride on public land to wear a helmet and complete a safety course. Organizations approved by the state Department of Public Safety could hold the courses.
Advocates for children's health have criticized the bill's narrow scope. They say Mississippi's death rate for ATV riders under 16 is significantly higher than the national rate.
Supporters say the new law is a "first step" in preventing injury on ATVs.
The bill is Senate Bill 2196.