Skip to main content
Find a Lawyer
Please enter a legal issue and/or a location
Begin typing to search, use arrow keys to navigate, use enter to select

What Are the Montana DUI Laws?

The state of Montana doesn't tolerate drugged or drunk driving. Montana overhauled its DUI laws in 2021 to make them tougher. If you're convicted of driving under the influence (DUI), you face jail time, hefty fines, and lengthy license suspensions. Montana couples its penalties with a substance abuse treatment program and required education courses to reduce repeat DUI offenses.

Montana decriminalized the possession of small amounts of cannabis in 2021. Montana amended its DUI law to recognize a legal limit for cannabis intoxication.

Driving with any level of impairment is dangerous. In 2020, 66% of traffic fatalities in Montana involved an impaired driver. Montana's law enforcement officers receive specialized training to look for impaired drivers.

Finding yourself charged with a DUI is stressful. You face heavy consequences. Learn more about what to expect below.

Blood Alcohol Concentration (BAC) Limits and Implied Consent

"Per Se" BAC Limit 0.08%
Zero Tolerance (Underage) BAC Limit 0.02%
Enhanced Penalty (Aggravated) BAC Limit 0.16%
Implied Consent to Submit to BAC Test? Yes

Select Penalties

Minimum License Suspension or Revocation (1st /2nd/ 3rd offense) 6 months/ 1 year / 1 year
Mandatory Alcohol Education, or Assessment and Treatment Both
Vehicle Confiscation Possible? Yes
Ignition Interlock Device Possible? Yes

Disclaimer: State laws are always subject to change through the passage of new legislation, ballot initiatives, rulings in the higher courts, including federal decisions, and by other means. While we strive to provide the most current information available, please consult an attorney or conduct your own legal research to verify the state laws you are researching.

Montana Driving Under the Influence Laws

Montana prohibits anyone from driving or being in actual physical control of a vehicle while under the influence of:

  • Alcohol
  • Delta-9-tetrahydrocannabinol (THC)
  • Any drug that causes impairment
  • A combination of drugs and alcohol

You are under the influence if your ability to operate a motor vehicle is diminished because of drugs, alcohol, or both.

Per Se DUI Offense

per se law sets a legal BAC limit at which you're legally intoxicated. If your blood alcohol content (BAC) is 0.08% or more, law enforcement will charge you with a per se DUI. This BAC limit is 0.04% if you are a commercial driver.

Montana also has a per se limit for delta-9-tetrahydrocannabinol (THC). THC is the active ingredient in cannabis or marijuana. Montana recognizes a THC level of 5 ng/ml in your blood as legally intoxicated.

Law enforcement doesn't need to provide evidence of your impairment. You may not feel intoxicated and may be driving carefully. If chemical tests show that your BAC is at least 0.08%, you will face arrest on a DUI charge. A valid chemical test is all the evidence law enforcement needs.

Law enforcement can still charge you with a DUI if your BAC is 0.04% to 0.07%. The officer needs additional evidence to show that you could not safely operate or control the vehicle because of your impairment.

Implied Consent Law

During a traffic stop, law enforcement can request chemical tests when they suspect you of driving intoxicated. By operating a vehicle within the state, the state deems you to have given consent to these tests.

Law enforcement will ask you to submit to a preliminary breath test or Breathalyzer when they think you may be driving intoxicated. They may also ask you to perform a series of field sobriety tests. Based on these results, the police officer can ask you to take a chemical test, such as a blood test, breath test, urine analysis, or an oral fluid test.

Under Montana's implied consent law, law enforcement expects you to cooperate with chemical testing, including the preliminary breath test. You may refuse, but there are immediate penalties. The police officer will confiscate your driver's license at the scene. The officer may still apply for a warrant to compel you to cooperate. Evidence of your refusal is admissible in court. The court or jury may infer your intoxication because of your refusal.

Implied Consent Refusal

For a first offense, the Montana Motor Vehicle Division will suspend your driving privileges for six months. A second offense within five years will suspend your license for one year. You will have to pay an administrative fee of $300 and reinstatement fees. You are not eligible for a restricted probationary license during your suspension period. This suspension is separate from your criminal charge, and you must serve it, even if the court acquits you or dismisses your charge.

Aggravated DUI

You may face an aggravated DUI charge if certain conditions are present:

  • Your BAC level is 0.16% or more
  • You have orders to operate a vehicle with an ignition interlock device
  • You have a revoked driver's license because of a prior DUI offense
  • You're under a license revocation because of a chemical test refusal

Penalties for an aggravated DUI conviction include at least two days in jail and at least a $1,000 fine. You must take part in a treatment court program if there is one in your area. You must also enroll in a 24/7 sobriety monitoring program.

DUI Penalties

A DUI is typically a misdemeanor charge for the first to third offense, so long as there are no aggravating factors. The court may not suspend mandatory minimum jail terms. Home confinement is not allowed as an alternative.

Everyone convicted of a DUI must complete a chemical dependency assessment before sentencing. The judge may add extra requirements to your sentence based on the assessment recommendations.

For a first-offense DUI conviction, your sentence can include:

  • Mandatory 24 consecutive hours in jail
  • Up to six months in jail possible
  • Fines of $600 to $1,000
  • Driver's license suspension for six months
  • Undergo a chemical dependency assessment
  • Completion of a chemical dependency education course

A second DUI conviction within 10 years will increase your penalties as follows:

  • Mandatory seven days in jail
  • One year in jail maximum possible
  • Fined between $1,200 and $2,000
  • Driver's license suspension for one year
  • Undergo a chemical dependency assessment
  • Complete an approved chemical dependency treatment program
  • Monthly sobriety monitoring for one year under the 24/7 program

Third DUI conviction:

  • Mandatory minimum of 30 days in jail
  • Up to one year of jail time is possible
  • Fines between $2,500 and $5,000
  • Driver's license suspension for one year
  • Undergo a chemical dependency assessment
  • Complete an approved chemical dependency treatment program
  • Monthly sobriety monitoring for one year under the 24/7 program

A fourth or subsequent offense is a felony charge.

Montana's DUI laws add enhanced penalties if you have a minor aged 16 or younger in your vehicle at the time of your DUI. Fines and mandatory jail time double.

Restricted Probationary License

After a first DUI conviction, you may request a restricted, probationary license during your sentencing. You will serve some of your suspension period. A judge may grant this license with the condition that you install an ignition interlock device (IID) in any vehicle you operate. The judge may not give a probationary license after subsequent DUIs unless you are participating in a DUI treatment court program.

A restricted probationary license only allows you to drive on a limited basis. For example, you may go to work, school, or to attend DUI treatment.

Ignition Interlock Device

An ignition interlock device (IID) connects to your vehicle's ignition system. You must provide a breath sample before you can drive. If the device detects alcohol, your vehicle will not start. The IID will randomly prompt you for extra samples during your drive to ensure you aren't drinking.

You will need to install an IID after a second DUI conviction if you're convicted of an aggravated DUI or you have a suspended license after refusing chemical testing. A judge will also order that you participate in a 24/7 sobriety monitoring program.

Treatment Courts

Sometimes called "DUI court," Montana's Treatment Court program may be an option for some facing DUI charges. The program has strict requirements for participants. You must comply with all treatment program requirements and undergo random drug and alcohol testing. These tests may be urine samples or through a blood draw.

If accepted, you must plead guilty to your DUI charge. The court will suspend your sentence minus the mandatory minimum jail time. If you fail to meet the program's requirements, the court will impose your suspended sentence.

Zero Tolerance for Underage DUI

Montana has a zero-tolerance law for underage DUIs. If you are under 21, you cannot have any measurable amount of alcohol in your system. If law enforcement finds you have a BAC of 0.02% or more, you will face a DUI charge. It takes very little alcohol to reach a BAC of 0.02%.

Penalties for a first DUI conviction as a minor include a fine of $100 to $500 and a 90-day license suspension. A second DUI will earn you a $200 to $500 fine and a six-month license suspension. If you are 18 or older, you could serve up to 10 days in jail.

All DUI convictions will require you to complete a chemical dependency education course and a chemical dependency assessment and treatment program.

Montana DUI Resources:

Consider Getting Legal Help With Your DUI Charges

An impaired driving conviction can have negative consequences beyond the actual sentence. The conviction remains on your criminal record for years. It can prevent you from getting a job or applying to college and increase your insurance rates significantly. If you're facing DUI charges in Montana, an attorney specializing in DUI defense will be able to review the facts of your case and plan a defense strategy. Get started today and contact a Montana DUI defense attorney near you.

Was this helpful?

You Don’t Have To Solve This on Your Own – Get a Lawyer’s Help

Meeting with a lawyer can help you understand your options and how to best protect your rights. Visit our attorney directory to find a lawyer near you who can help.

Or contact an attorney near you:

Next Steps: Search for a Local Attorney

Contact a qualified attorney.

Begin typing to search, use arrow keys to navigate, use enter to select

Can I Solve This on My Own or Do I Need an Attorney?

  • Complex DUI situations usually require a lawyer
  • DUI defense attorneys can challenge Breathalyzer/Intoxilyzer or blood test results
  • A lawyer can seek to reduce or eliminate DUI penalties
  • A lawyer can help get your license back

Get tailored advice and ask your legal questions. Many attorneys offer free consultations.


 If you need an attorney, find one right now.

Copied to clipboard

Find a Lawyer

More Options