Montana Car Seat Laws: Requirements and Guidelines

Montana law sets a four-stage child safety restraint requirement under MCA 61-9-420: rear-facing for children under 2, rear-facing or forward-facing with an internal harness for ages 2 to under 4, forward-facing harness or a booster seat secured with a lap-shoulder belt for ages 4 to under 8, and an adult seat belt once a child turns 9 or outgrows the booster seat's manufacturer limits, whichever comes first. The Montana Highway Traffic Safety Division also recommends children remain in the back seat until age 13.

What Are the Height and Weight Requirements for Car Seats in Montana?

Montana law sets a four-stage child safety restraint requirement under MCA 61-9-420, most recently amended in 2025.

Children under 2 years old must ride in a rear-facing child safety restraint system.

Children ages 2 to under 4 must ride in a rear-facing or forward-facing restraint with an internal harness.

Children ages 4 to under 8 must ride in a forward-facing restraint with an internal harness, or a booster seat secured with a lap-shoulder belt.

A child may use an adult seat belt alone once they turn 9 years old or outgrow the booster seat's manufacturer height or weight limits, whichever comes first.

The Montana Highway Traffic Safety Division separately recommends children sit in the back seat until they are 13 years of age.

What Are the Rear Facing Car Seat Laws in Montana?

Montana law requires children under 2 years old to ride in a rear-facing child safety restraint system that complies with federal motor vehicle safety standards (MCA 61-9-420). The AAP (American Academy of Pediatrics) recommends children remain rear-facing for as long as possible, even beyond age 2, up to the manufacturer's maximum weight and height limits.

The two types of rear-facing seats that are mainly used are infant-only and convertible seats. Infant-only is perfect for newborns, whereas convertible seats allow you to keep your baby rear-facing for a longer period (often up to age 4) since they can support up to 40 pounds. The seat usually comes equipped with a harness. This helps to keep your baby in position during a car crash to protect the delicate body parts (neck, head, and spine). Always secure your baby in the back seat together with the seat's harness according to the manufacturer's instructions.

What are the Forward Facing Car Seat Laws in Montana?

Montana law allows children ages 2 to under 4 to ride in a rear-facing or forward-facing restraint with an internal harness, and requires children ages 4 to under 8 to use a forward-facing harness seat or a booster seat secured with a lap-shoulder belt (MCA 61-9-420). For those using convertible seats, once a child has outgrown the rear-facing position, it is safe to turn the seat to face forward.

A child should remain in a forward-facing harness seat until he or she has exceeded the age, weight, and height limits set by the manufacturer. With some seats accommodating kids of up to 65 pounds, children can safely remain forward-facing until age 7 or beyond. Using a 5-point harness with a tether is the best way to fasten your child in the seat. The harness straps should be snug above the child's collarbone. Also, if a child's ears are at the same level as the top of the seat or when the shoulders are higher than the topmost slot, then this means the child is big enough to transition to a booster seat.

What Are the Booster Seat Laws in Montana?

Montana law requires children ages 4 to under 8 to ride in a forward-facing harness seat or a booster seat secured with a lap-shoulder belt, once they have exceeded the manufacturer's height and weight limits for a forward-facing harness seat (MCA 61-9-420). There are two different types of booster seats, high-back and backless. If your car does not have a headrest to support your child's head and neck, then using a high back is recommended. If your car's seat is long enough to hold your child's head, you can use a backless one.

Booster seats should be secured with lap-shoulder belts, never with a lap-only belt. Make sure the lap portion lies flat across the upper thighs, and the shoulder portion lies snug across the middle of the chest area.

Montana law allows a child to move to an adult seat belt alone once they turn 9 years old or outgrow the booster seat's manufacturer height or weight limits, whichever comes first. Most experts also point to a height of 4'9'' (attained at age 8-12) as a useful benchmark, since safety belts are designed to fit passengers of that height or taller. A child can be considered seat belt ready if he or she can sit straight against the back of the seat without slouching and if the knees are bent at the edge of the seat, with feet touching the floor.

What Are the Requirements For a Child to Use the Front Seat in Montana?

The law does not cover anything to do with front seat regulations. However, the Montana Highway Traffic Safety Division says children should sit in the back seat until they are 13 years of age. This is in line with AAP's recommendation which also says passenger-side airbags in the front seat can be lethal to children due to the great force with which they deploy. They further advise that the back seat is generally safer for children.

Is it Illegal to Leave a Child Inside a Vehicle in Montana?

There is no law regarding leaving a child unattended inside a car, however, you can be charged with negligence if the child gets hurt. It is recommended to never leave your child unattended for any length of time.

Is it Illegal to Smoke In a Car With a Child in Montana?

It is not illegal to smoke in a car with child passengers in Montana.

Are Car Seats Required in Taxis in Montana?

The law is not clear as to whether commercial vehicles such as taxis are required to comply with the state's car seat laws. Children who have been certified by a physician as to having a disability, medical, or physical condition that makes it unsuitable to use child restraint devices are exempted.

What Is the Law on Car Seat Replacement in Montana?

Montana does not have a law specifically related to car seat replacement. However, The Montana Department of Transportation recommends parents should replace their car seats after an accident. Safety experts say you should replace your car seat after a second accident. This is because car seats can develop tiny fractures that are hard to spot, so using them after a crash may not be safe. Also, car seats usually have expiry dates (about 6 years), so be sure to check if yours is past the expiry date.

More Montana Laws

• Montana Car Accident Laws