San Marcos, TX ZIP Codes
San Marcos, Texas has 2 ZIP codes: for street addresses and for PO boxes.
Mail addressed to San Marcos covers nearby places too.
Where the 78666 ZIP code reaches
Tap or point to an area to see its ZIP code.Full-size map
78667 has no area on the map: it is a PO box or single-organization ZIP code. Dashed line: San Marcos city limits.
Map: Census Bureau ZIP Code Tabulation Areas (2020) and place limits (2024).
Check an address in San Marcos
Street ranges from the Census Bureau, 2026. PO box and organization ZIP codes are not found by street. A new street may be missing: address not found?
San Marcos PO box and business ZIP codes
| ZIP | Type and post office or station |
|---|---|
| 78666 | street delivery San Marcos Annex |
| 78667 | PO boxes at the San Marcos post office San Marcos |
ZIP codes from nearby towns that reach into San Marcos
- 78656, mailing town Maxwell, covers 9 percent of San Marcos
Why your mail may say San Marcos when you live outside it
San Marcos ZIP codes also cover Kyle and Redwood, so a letter addressed to San Marcos can go to a home outside the city limits.
The reverse happens too: parts of San Marcos use 78656, which mails under a neighboring town's name.
A ZIP code does not set your city, school district or tax. Hays County property records show which city you are in.
San Marcos ZIP code questions
What is the main ZIP code for San Marcos?
78666, the ZIP code of the main San Marcos Annex post office at 210 S Stagecoach Trl.
Which San Marcos ZIP codes are for PO boxes only?
78667. Mail to it goes to boxes at the post office, not to street addresses.
What county is San Marcos in?
Hays County, with parts in Caldwell County and Guadalupe County.
ZIP codes for towns near San Marcos
More towns near San Marcos: Austin, Timberwood Park, Pflugerville, Cedar Park, San Antonio, Round Rock, Leander, Hutto, Georgetown.
Sources and last checked
USPS ZIP Locale Detail (October 1, 2026), GeoNames (CC BY 4.0), U.S. Census Bureau, HUD-USPS crosswalk.
Checked October 20, 2026. Sources · How we build our lists · Corrections