Mount Sinai Post Office

457 Route 25a, Mount Sinai, NY 11766

Contact Numbers

Phone: 631-928-0394
Fax: 631-476-3512
TTY: 877-889-2457
Toll-Free: 1-800-Ask-USPS® (275-8777)

Retail Hours

Lobby Hours
PO Box Access Available

Monday 5:30am - 5:30pm
Tuesday 5:30am - 5:30pm
Wednesday 5:30am - 5:30pm
Thursday 5:30am - 5:30pm
Friday 5:30am - 5:30pm
Saturday 5:30am - 3:30pm
Sunday Closed

Last Collection Times

Monday 5:00pm
Tuesday 5:00pm
Wednesday 5:00pm
Thursday 5:00pm
Friday 5:00pm
Saturday 1:00pm
Sunday Closed

Bulk Mail Acceptance Hours

Monday 9:00am - 2:00pm
Tuesday 9:00am - 2:00pm
Wednesday 9:00am - 2:00pm
Thursday 9:00am - 2:00pm
Friday 9:00am - 2:00pm
Saturday Closed
Sunday Closed

*This facility does not process US Passports applications or renewals. Check nearby locations below.

  • Bulk Mail Acceptance
  • Bulk Mail Account Balance
  • Bulk Mail New Permit
  • Burial Flags
  • Business Line
  • Business Reply Mail Account Balance
  • Business Reply Mail New Permit
  • Duck Stamps
  • General Delivery
  • Money Orders (Domestic)
  • Money Orders (Inquiry)
  • Money Orders (International)
  • Packaged Stamps
  • Pickup Accountable Mail
  • Pickup Hold Mail
  • PO Box Online
  • Lot Parking

Visit our Links Page for Holiday Schedule, Change of Address, Hold Mail/Stop Delivery, PO Box rentals and fees, and Available Jobs.

*Please call to verify information. Is anything incorrect? Let us know here

Nearby Post Offices:

Miller Place
47 Echo Ave
0.9 mile away

Port Jefferson Station
544 Jefferson Plz
1.3 miles away

Port Jefferson
407 E Main St Ste 17
1.9 miles away

Sound Beach
25 New York Ave
2.2 miles away


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Not getting mail delivered and being sent on time, missing delivery days, putting the box key in the wrong mail box or not at all, having Amazon claim it was delivered...missing mail for over 3 months that neighbors received but we did not. Not sending or losing our checks at the post office that we mailed to pay bills and than incurring late fees or cancellations.


My postal carrier is the very best; what more can I say. Allways cheerful, always right there with the mail. We are all fortunate to have him. He is greatly appreciated.


Yo hable para ver sobre un pedido y no hablan español Y de un solo. Me colgaron

* is not a part of, or affiliated with, the official United States Postal Service (USPS).