Listed by Great Island Realty LLC · Janet Sylvester · 603-433-3350
Single Family Residence · New Castle, NH
350 Portsmouth Avenue, New Castle, NH
$3,750,000
$3,950,000 · changed Oct 16, 2026
Est. $18,962/mo · 20% down, 30-yr, 6.5% (Owl’s Nest Real Estate estimate, not MLS data)
- Beds
- 3
- Baths
- 4
- Sq Ft
- 2,375
- Built
- 1977
- MLS®
- #5107161
Property Description
350 Portsmouth Avenue sits in New Castle, New Hampshire — a single-family home offering 3 bedrooms, 4 bathrooms and 2,375 square feet of living space. The asking price is $3,750,000. The format is the classic one — a standalone home with no association between you and your plans for it. Beyond the basics, the listing carries a 0.25-acre lot, garage parking for 2 and 1977 construction. See the listing's full details below, and reach out for a private showing of 350 Portsmouth Avenue.
Welcome to 350 Portsmouth Avenue, an exceptional waterfront residence offering a front row seat to one of the most captivating maritime settings on the New Hampshire Seacoast. With expansive water views of the Piscataqua River and Back Channel, this remarkable property captures everything that makes New Castle waterfront living so special. From magnificent ships and iconic Portsmouth tugboats to sailboats, fishing vessels and pleasure craft, the ever changing boat traffic provides a spectacular backdrop from morning until night. A private deep water dock makes this a dream for boating enthusiasts, offering direct access to Portsmouth Harbor, the Piscataqua River and the open Atlantic. Adding to the property's unique appeal is deeded access to the Back Channel, creating a wonderful launching point for kayaks and paddleboards. Designed to embrace this extraordinary setting, the home features multiple waterfront decks for entertaining, outdoor dining or simply watching the river come alive. A walk-out lower level extends the living space outdoors, while the hot tub and sauna create a private waterfront retreat to enjoy throughout the seasons. Enjoy all the amenities that make New Castle one of the Seacoast's most coveted communities, the nearby yacht clubs, Wentworth Marina, Wentworth by the Sea Country Club, Great Island Common, beaches and the historic charm of island living, all just minutes from downtown Portsmouth. And with New Castle's exceptionally low property taxes, this is a rare opportunity to combine an extraordinary waterfront lifestyle with one of New Hampshire's most desirable communities. Deep water boating out your front door. Kayaking and paddleboarding from your deeded Back Channel access. Incredible water views, spectacular boat traffic, waterfront decks, hot tub and sauna, all in the heart of New Castle. 350 Portsmouth Avenue isn't simply a waterfront home, it's a lifestyle defined by the water.
Location Highlights
350 Portsmouth Avenue is a single family residence in New Castle, New Hampshire, listed at $3,750,000. That works out to about $1,579 per square foot, for a home built in 1977. It has been on the market for 2 months.
At this latitude, New Castle averages roughly 8.4 hours of sun a day in June and 3.6 in December.
Zoned schools in the New Castle: Maude H. Trefethen School (Elementary), Rye Junior High School (Middle), Portsmouth (High). Always confirm zoning with the district office.
Source: zoned school names are PrimeMLS listing data; distances, sun exposure and school facts are Owl’s Nest Real Estate additions (school facts from the NCES, U.S. Department of Education) — not PrimeMLS data.
Property Details
Essentials & finishes
- Bedrooms
- 3
- Total Baths
- 4
- Full Baths
- 1
- SqFt
- 2,375
- Price / SqFt
- $1578.95
- Property Type
- Single Family Residence
- Year Built
- 1977
- County
- NH-Rockingham
- Town
- New Castle, NH
- Status
- Active
- Days on Market
- 51
Primary Features
- County
- NH-Rockingham
- Property Type
- Residential
- Year Built
- 1977
- Zoning
- RD RE
Interior Features
- Appliances
- Electric Cooktop, Dishwasher, Double Oven, Wall Oven, Refrigerator
- Basement
- Yes
- Basement Access Type
- Walkout
- Basement Description
- Climate Controlled, Daylight, Full, Partially Finished, Interior Stairs, Walk-Out Access
- 1/4 Baths
- 0
- 3/4 Baths
- 2
- Cooling
- Central Air
- Electric
- 200+ Amp Service
- Flooring
- Carpet, Tile
- Heating
- Forced Air, Oil
- Interior Features
- Cathedral Ceiling(s), Ceiling Fan(s), Dining Area, Wood Fireplace, 1 Fireplace, Kitchen Island, Primary BR w/ BA, Natural Light
- Rooms - Total
- 7
- SqFt-Approximate Finished Above Grade
- 2,375
- SqFt-Approximate Finished Below Grade
- 863
- SqFt Approximate Total Finished
- 3,238
- SqFt Approximate Total
- 4,181
Location Information
- School - District
- New Castle
- School - Elementary
- Maude H. Trefethen School
- School - High
- Portsmouth
- School - Middle/Jr
- Rye Junior High School
Financial Details
- Cable Company
- Xfinity
- Electric Company
- Eversource
- Fuel Company
- Nobel Fuel
- Tax - Gross Amount
- $15,636
- Tax Year
- 2025
- Taxes TBD
- No
Additional
- Construction Status
- Existing
- Construction
- Wood Frame, Wood Siding
- Covenants
- No
- Flood Zone
- Land Only
- Pre-Construction
- No
- Property Sub Type
- Single Family Residence
- Seasonal
- No
- Total Stories
- Two
- Surveyed
- Unknown
- Timeshare/Fractional Ownership
- No
- Water Access Details
- Deep Water Access, Dock Access
External Features
- Color
- Gray
- Driveway
- Paved
- Exterior Features
- Boat Mooring, Boat Slip, Hot Tub, Private Dock, Sauna
- Foundation
- Poured Concrete
- Garage
- Yes
- Garage Capacity
- 2
- Lot Features
- Landscaped, Near Country Club, Near Golf Course, Near Shopping, Near School(s)
- Lot - Acres
- 0.25
- Lot - SqFt
- 10,890
- Parking
- Attached, Auto Open, Direct Access, Driveway
- Road Frontage Type
- Paved, Public Maintained Road
- Road Frontage
- Yes
- Road Frontage Length
- 100
- Roof
- Asphalt Shingle
- Sewer
- Public
- Utilities
- Cable
- Water Source
- Public
- Water Body Type
- River
MLS®: PrimeMLS #5107161; Listed by Great Island Realty LLC · Janet Sylvester · 603-433-3350
Property History
Estimated annual taxes for this property
- 2024
- $63,750
- 2023
- $62,156
- 2022
- $60,563
Source: Owl’s Nest Real Estate estimate from the list price at New Hampshire’s average effective tax rate — not PrimeMLS or town assessor data. Verify with the town assessor.
Market Data
Live snapshot computed by Owl’s Nest Real Estate from PrimeMLS IDX active listings in this town
- Active listings in New Castle
- 2
- Average list price
- $2,400,000
- Price range
- $2,400,000 – $2,400,000
Mortgage Calculator
Estimate your monthly payment for this home
Estimated Monthly Payment
$25,056/ mo
- Principal & Interest
- $18,962
- Property Tax
- $5,313
- Home Insurance
- $781
Source: Owl’s Nest Real Estate estimate, not PrimeMLS data. Estimates use typical New Hampshire costs — a 1.7% effective property-tax rate, insurance at 0.25% of home value/yr, and PMI below 20% down. Actual town tax rates vary; verify with your lender and the town assessor.
Around This Property
Schools, everyday places and nearby destinations near 350 Portsmouth Avenue, New Castle, NH
Assigned Schools
- Elementary
- Maude H. Trefethen School
- Middle
- Rye Junior High School
- High School
- Portsmouth
- District
- New Castle
Source: Google Maps Platform (Places) and Owl’s Nest Real Estate — not PrimeMLS data.
Questions About This Listing
How big is 350 Portsmouth Avenue?
350 Portsmouth Avenue in New Castle, NH has 3 bedrooms and 4 bathrooms (1 full, 2 three-quarter and 1 half) in 2,375 square feet of finished living space.
Counting 863 finished square feet below grade, the MLS lists 3,238 finished square feet in total.
What is the asking price of 350 Portsmouth Avenue?
350 Portsmouth Avenue in New Castle, NH is listed for $3,750,000 on PrimeMLS.
That is about $1,579 per square foot of finished living space.
It came on the market on August 28, 2026.
Is 350 Portsmouth Avenue on the water?
Yes. The MLS lists 350 Portsmouth Avenue in New Castle, NH as a waterfront property on a river.
Water access: deep water access and dock access.
The MLS lists a private dock.
Confirm frontage, shoreland rules and any dock or beach rights during due diligence.
What schools serve 350 Portsmouth Avenue?
The MLS places 350 Portsmouth Avenue in New Castle, NH in the New Castle school district.
Listed schools: Maude H. Trefethen School (elementary), Rye Junior High School (middle) and Portsmouth (high).
School assignments can change; confirm with the district.
Is 350 Portsmouth Avenue still available?
Yes. 350 Portsmouth Avenue in New Castle, NH is listed as Active on PrimeMLS (MLS #5107161).
Status can change quickly; contact us to confirm availability before you visit.
Who is the listing agent for 350 Portsmouth Avenue?
350 Portsmouth Avenue in New Castle, NH is listed by Janet Sylvester of Great Island Realty LLC (603-433-3350).
Owl's Nest Real Estate shows it through the PrimeMLS IDX feed; we are not the listing brokerage.
What kind of property is 350 Portsmouth Avenue?
350 Portsmouth Avenue in New Castle, NH is a single-family home built in 1977.
The MLS lists its style as Contemporary, with two stories.
Where is 350 Portsmouth Avenue located?
350 Portsmouth Avenue is in New Castle, New Hampshire 03854, in Rockingham County.
Location notes from the MLS: near country club, near golf course, near shopping and near school(s).
How much land comes with 350 Portsmouth Avenue?
350 Portsmouth Avenue in New Castle, NH sits on 0.25 acres, per the MLS.
The lot is described as landscaped.
It has 100 feet of road frontage (paved and public maintained road).
Zoning: RD RE.
How much are the property taxes on 350 Portsmouth Avenue?
Annual property taxes on 350 Portsmouth Avenue in New Castle, NH are $15,636 for the 2025 tax year, per the MLS.
New Hampshire towns set their own tax rates and revalue periodically, so confirm the current bill with the New Castle assessing office.
How is 350 Portsmouth Avenue heated?
350 Portsmouth Avenue in New Castle, NH is heated by forced air and oil, per the MLS.
Cooling: central air.
Does 350 Portsmouth Avenue have town water and sewer?
350 Portsmouth Avenue in New Castle, NH has public water and public sewer, per the MLS.
MLS details — water: public; sewer: public.
Electric: 200+ amp service (Eversource).
Other utilities: cable; cable provider Xfinity.
Is there a basement at 350 Portsmouth Avenue?
Yes. 350 Portsmouth Avenue in New Castle, NH has a basement with walkout access, including 863 finished square feet.
The MLS describes it as climate controlled, daylight, full, partially finished, interior stairs and walk-out access.
What features does 350 Portsmouth Avenue have?
Inside, the MLS lists these features at 350 Portsmouth Avenue in New Castle, NH: cathedral ceiling(s), ceiling fan(s), dining area, wood fireplace, 1 fireplace, kitchen island, primary BR w/ BA and natural light.
Outside: boat mooring, boat slip, hot tub, private dock and sauna.
Flooring: carpet and tile.
Listed appliances: electric cooktop, dishwasher, double oven, wall oven and refrigerator; confirm which ones convey in the purchase agreement.
Does 350 Portsmouth Avenue have a garage?
350 Portsmouth Avenue in New Castle, NH has a 2-car garage and a paved driveway.
Parking details: attached, auto open, direct access and driveway.
How do I schedule a showing of 350 Portsmouth Avenue?
To see 350 Portsmouth Avenue in New Castle, NH, use Request a Showing on this page or call Owl's Nest Real Estate at 401-648-5308.
We can show any MLS-listed home and represent you as your buyer's agent; the listing brokerage represents the seller.
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NOTE: This representation is based in whole or in part on data generated by PrimeMLS, Inc., which assumes no responsibility for its accuracy. The data relating to real estate displayed on this site comes in part from the IDX Program of PrimeMLS.
This listing data is intended for consumers’ personal, non-commercial use and may not be used for any purpose other than to identify prospective properties consumers may be interested in purchasing. Data last updated 11/03/26.