Replacing or Upgrading Your Mailbox Lock: What You Need to Know
Most mailbox locks fail for one of three reasons: the key breaks, the cylinder wears out, or the lock gets forced open. Here's how to choose the right replacement and what to look for before you buy.
Cam Lock vs High-Security Lock: What's the Difference?
The vast majority of residential mailboxes use a cam lock — a cylindrical lock with a rotating metal plate at the back. They're cheap, easy to replace, and available in two standard sizes: 5/8 inch and 3/4 inch diameter. Measure your existing lock before ordering to make sure you get the right fit. Our Cam Lock for Mailbox fits most standard residential mailboxes and ships within 24 hours.
High-security cam locks use a more complex pin configuration that makes them significantly harder to pick or drill. If you live in an area with frequent mail theft or receive checks and sensitive documents regularly, our High Security Mailbox Lock is worth the upgrade. If you're also looking to upgrade your mailbox's appearance, check out our Mailbox Flag collection for a complete exterior refresh.
Keyless and Digital Options
If you're tired of carrying yet another key, a keyless mailbox lock is a practical alternative. Our Digital Lock for Mailbox uses a push-button combination code — no key required, no lockout risk if you lose it. It runs on a standard battery and fits most standard mailbox door thicknesses between 1 and 2 inches. For a simpler keyless option, the Keyless Mailbox Lock is our most popular choice in this category.
How to Know Which Lock Fits Your Mailbox
Before buying a replacement lock, check three measurements on your current lock: the diameter of the cylinder, the length of the cam, and the thickness of the mailbox door panel. Most standard US residential mailboxes take a 5/8 inch cam lock with a 3/4 inch cam length. Cluster mailboxes and USPS-style CBU units typically use a different format — check your mailbox model number if you're unsure. Our Mailbox Key and Lock comes with two keys included and fits the most common residential formats.
How to Replace a Mailbox Lock in 5 Minutes
You need two tools: a flathead screwdriver and a small wrench. Open the mailbox door, locate the retaining nut at the back of the lock cylinder, and unscrew it. Pull the old lock out from the front. Insert the new lock, thread the retaining nut back on from behind, and tighten. Close the door and test the key. That's it — no locksmith required.
When to Replace vs When to Rekey
Rekeying a mailbox lock only makes sense if the cylinder is in good condition and you simply need to change the key — for example after moving into a new home. If the lock is worn, stiff, or has been tampered with, replace it entirely. A new cam lock costs between $14 and $25 and takes five minutes to install — there's rarely a reason to rekey rather than replace.
FAQ
What size cam lock do I need for my mailbox?
The two most common sizes are 5/8 inch and 3/4 inch diameter. Measure the hole in your mailbox door or remove the existing lock and check the diameter printed on the cylinder body.
Can I replace my mailbox lock myself?
Yes. Standard cam lock replacement requires only a screwdriver and a wrench and takes about five minutes. No locksmith needed.
My key turns but the mailbox won't open — what's wrong?
The cam at the back of the lock is likely broken or has slipped out of position. Remove the lock, check that the cam is properly attached to the cylinder, and reinstall. If the cam is cracked or bent, replace the lock entirely.
Are your locks compatible with USPS cluster mailboxes?
Standard cam locks fit most residential curbside mailboxes. CBU cluster units and apartment mailboxes use a different lock format — contact us with your mailbox model number and we'll confirm compatibility before you order.