Can I Carry a Knife in Massachusetts? Blade Limits and Penalties

Yes, you can carry a knife in Massachusetts, but the state bans several specific designs outright and can treat almost any knife as an illegal weapon depending on the circumstances of an arrest. The controlling statute is MGL c. 269, § 10(b). It lists prohibited knives by category, sets a blade-length limit for automatic knives, and gives prosecutors a separate route to charge a weapons offense when an otherwise legal knife is present during a disturbance.¹

Knives You Cannot Carry at All

Section 10(b) prohibits carrying the following knives on your person or in a vehicle, no matter your reason:

Daggers and dirk knives
Stilettos
Double-edged knives (sharpened on both sides of the blade)
Ballistic knives (with a detachable blade that can be propelled by a spring or other mechanism)
Any sheath or case designed to let you draw a locking-blade knife already in the locked, open position

These categories turn on design, not size. A three-inch double-edged blade is treated the same as a ten-inch one. Possession itself is the offense, so a statement that you did not intend to use the knife as a weapon is not a defense.¹

Automatic Knives and the 1.5-Inch Blade Limit

Automatic knives (commonly called switchblades) have their own rule, and it’s where people most often go wrong. Section 10(b) prohibits carrying a knife with an automatic spring-release mechanism that opens the blade from the handle if the blade is longer than one and a half inches.¹

Anything at or under an inch and a half falls outside the ban. That’s a short blade, and most commercially sold switchblades exceed it. Measure carefully from the handle to the tip. A fraction over the limit is a felony-level offense.

Spring-assisted knives that require manual pressure on the blade itself, rather than a button on the handle, are generally not considered automatic knives under the statute. The federal Switchblade Act similarly excludes knives with a blade bias toward closure.²

When an Ordinary Knife Becomes a “Dangerous Weapon”

A standard folding knife, a fixed-blade hunting knife, or a utility blade is legal to own and carry in Massachusetts. Section 10(b) contains a second clause, though: if you are arrested on a warrant or during a breach of the peace and you have a knife on you, that knife can be classified as a “dangerous weapon,” and you face the same penalties as someone carrying a banned dagger.¹

Massachusetts courts decide whether an item qualifies by looking at how it was used or carried, not the owner’s stated intent. The relevant factors are the circumstances of the situation, the size and shape of the knife, and the way it was handled. A box cutter clipped to a carpenter’s belt reads differently from the same box cutter found on someone arrested during a bar fight.

There is no statewide blade-length limit for ordinary knives. A five-inch folding knife carried for everyday use is legal. But context matters, and the statute gives prosecutors wide discretion to charge a weapons offense whenever a knife is present during an arrest.

Places Knives Are Off-Limits

Some locations ban knife possession even when the knife itself is otherwise legal. Under state law, the biggest one is schools: carrying any dangerous weapon on the grounds or inside any elementary school, secondary school, college, or university building is a crime unless you have written permission from the institution’s governing board or officer.¹

Federal law adds its own layer. Knives are prohibited in federal courthouses and federal buildings under 18 U.S.C. § 930. The TSA bans all knives from carry-on luggage at airports, though a knife can go in checked baggage if it is sheathed or securely wrapped.³ Amtrak is stricter: knives are banned from both carry-on and checked baggage on trains.⁴

Penalties Under Section 10(b)

A first offense carries two and a half to five years in state prison, or six months to two and a half years in a jail or house of correction. If the court finds no prior felony convictions, a lighter alternative is available: a fine of up to $50 or up to two and a half years in jail.¹

Repeat convictions escalate quickly and carry mandatory prison time that cannot be suspended, reduced for good behavior, or converted to probation:

Second offense: five to seven years in state prison
Third offense: seven to ten years in state prison
Fourth offense: ten to fifteen years in state prison

A judge has no authority to go below these minimums, and you serve the full sentence without early release.¹

Carrying a dangerous weapon on school or university grounds is punished separately: a fine of up to $1,000, up to two years of imprisonment, or both.¹

Passing Through the State

There is no federal “safe passage” law that protects knife owners traveling through restrictive states. If you drive through Massachusetts with a knife that violates § 10(b), you face the same penalties as a resident.

Local Rules Can Be Stricter

Massachusetts has no statewide preemption law preventing cities and towns from writing their own knife restrictions. Boston and other larger cities may have local ordinances that go further than § 10(b). Before carrying a knife in any Massachusetts municipality, check the local rules. A knife that is legal under state law can still violate a city or town bylaw.

1
General Court of Massachusetts. Massachusetts Code 269-10 – Carrying Dangerous Weapons
2
Office of the Law Revision Counsel. 15 USC 1241 – Definitions
3
Transportation Security Administration – TSA.gov. Knives
4
Amtrak. Items Prohibited in Baggage Onboard the Train