ZIP Codes in Castro Valley, CA
Castro Valley uses 2 ZIP codes, all in Alameda County. Pick one below for details, or look up the full nine-digit ZIP+4 for a specific street address.
All 2 Castro Valley ZIP codes
| ZIP | Type | County | Population |
|---|---|---|---|
| 94546 | standard | Alameda | 44,855 |
| 94552 | standard | Alameda | 14,506 |
Finding a ZIP+4 in Castro Valley
Knowing which of these 2 ZIP codes covers an address only gets you partway. The four-digit extension identifies the specific delivery point — typically one side of one block. Two houses facing each other on the same Castro Valley street almost always have different ZIP+4 codes even though they share all five leading digits.
Appending ZIP+4 to a mailing list?
Upload a CSV of Castro Valley addresses and download it complete.