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For sale
  • $18,500,000

    631 N Mashta Drive, Key Biscayne, FL 33149

    4beds
    2,255sqft
    : 
    $133,070/mo
    Get pre-qualified
    Single Family Residence
    Built in 1958
    0.34 Acres Lot
    $16,585,700 Zestimate®
    $8,204/sqft
    $-- HOA

    What's special

    Spectacular waterfront settingPrivate dockDirect biscayne bay accessDesigner finishesBeautifully appointed bedroom suitesExceptional privacyExpansive backyard
    BRING ALL OFFERS! Exceptional waterfront opportunity in prestigious Key Biscayne. Set on a 15,000 sq. ft. lot with 100 feet of water frontage, this residence offers open-water views, direct Biscayne Bay access, and no fixed bridges to the ocean. Currently undergoing a complete renovation, it will feature modern finishes, impact windows and doors, new systems, spacious living areas, a chef's kitchen, and luxurious bathrooms. Enjoy a private dock, deep-water access, pool, breathtaking sunsets, and an unmatched boating lifestyle in one of South Florida's most desirable communities One of the most compelling waterfront opportunities currently available in all of Key Biscayne. Perfectly positioned on the exclusive and highly coveted Mashta Island, this exceptional property offers approximately 100 feet of prime waterfront, deep-water dockage, direct Biscayne Bay access, and no fixed bridges to the Atlantic Ocean, creating an unparalleled opportunity for boating enthusiasts and yacht owners. Mashta Island has long been recognized as one of South Florida's most prestigious residential enclaves, offering exceptional privacy, quiet tree-lined streets, oversized waterfront estates, and immediate access to the open waters of Biscayne Bay while remaining only minutes from Brickell, Downtown Miami, Coconut Grove, Coral Gables, Miami Beach, and Miami International Airport. Very few neighborhoods offer this combination of island living, security, boating lifestyle, and proximity to the city's financial and cultural centers. The residence is currently on renovation designed to transform the property into a contemporary waterfront estate while preserving the exceptional value of its location and oversized waterfront parcel. This is substantially more than a cosmetic renovation. The project includes major improvements throughout the residence, including redesigned living spaces, upgraded electrical and plumbing systems, new HVAC equipment, impact-resistant windows and doors, premium flooring, modern architectural lighting, designer finishes, and a completely reimagined interior intended to meet today's luxury lifestyle expectations. Upon completion, the home is anticipated to offer spacious entertaining areas, beautifully appointed bedroom suites, bathrooms, an impressive chef's kitchen featuring custom cabinetry, premium appliances, elegant countertops, and thoughtfully designed indoor-outdoor living spaces that maximize the spectacular waterfront setting. The property's exceptional orientation provides beautiful water views and unforgettable sunsets while creating an ideal environment for entertaining, family gatherings, and year-round outdoor living. The expansive backyard offers generous space surrounding the swimming pool together with multiple areas for outdoor dining, lounging, and enjoying the waterfront lifestyle that has made Key Biscayne one of the most desirable residential communities in South Florida. For boating enthusiasts, few properties can offer the combination of oversized waterfront, private dockage, deep-water access, and unrestricted navigation to Biscayne Bay and the Atlantic Ocean without fixed bridges. Whether accommodating a large sport yacht, cruising yacht, center console, or multiple vessels, the waterfront configuration provides flexibility rarely available in today's market. Key Biscayne continues to be recognized as one of South Florida's most exclusive island communities, celebrated for its pristine beaches, excellent schools, private clubs, marinas, tennis facilities, parks, bicycle paths, restaurants, and relaxed coastal lifestyle. Residents enjoy the unique advantage of living within a peaceful island environment while remaining only a short drive from Miami's world-class shopping, fine dining, cultural institutions, private airports, international business centers, and professional sports venues. The supply of premium waterfront homes on Mashta Island remains extremely limited due to the neighborhood's established character and finite number of waterfront parcels. As a result, opportunities to acquire large waterfront lots with substantial dockage and direct ocean access continue to be highly sought after by both domestic and international buyers. The combination of location, waterfront dimensions, boating accessibility, oversized lot, and comprehensive renovation creates a property with exceptional long-term appeal. Showings are strictly by appointment with the Listing Agent.. All measurements, dimensions, lot size, square footage, waterfront frontage, dock dimensions, room sizes, zoning, taxes, permits, specifications, plans, renderings, and property information are believed to be accurate but are not guaranteed and should be independently verified by Buyer. Renderings, conceptual plans, floor plans, specifications, and construction updates are available upon request when applicable. This offering represents an extraordinary opportunity to secure one of Key Biscayne's waterfront residences . Whether as a primary residence, seasonal retreat, or long-term investment, this property combines one of South Florida's most desirable locations with an outstanding boating lifestyle and exceptional future value. Bring All Offers.
    51 days
    686
    16

    Zillow last checked:

    Listing updated:

    Listed by:

    Javier Gustavo Quiroz 305-909-5940,

    Coldwell Banker

    Source: BeachesMLS,MLS#: B26058354MLS LogoOriginating MLS: BeachesMLS

      Facts & features

      Interior

      Bedrooms & bathrooms
      • Bedrooms: 4
      • Bathrooms: 5
      • Full bathrooms: 4
      • 1/2 bathrooms: 1
      • Main level bathrooms: 4
      • Main level bedrooms: 4
      Primary bedroom
      • Level: Main
      • Area: 500
      • Dimensions: 25 X 20
      Primary bedroom
      • Level: Main
      • Area: 500
      • Dimensions: 25 X 20
      Dining room
      • Level: Main
      • Area: 168
      • Dimensions: 12 X 14
      Dining room
      • Level: Main
      • Area: 168
      • Dimensions: 12 X 14
      Kitchen
      • Level: Main
      • Area: 132
      • Dimensions: 12 X 11
      Kitchen
      • Level: Main
      • Area: 132
      • Dimensions: 12 X 11
      Living room
      • Level: Main
      • Area: 352
      • Dimensions: 16 X 22
      Living room
      • Level: Main
      • Area: 352
      • Dimensions: 16 X 22
      Heating
      • Central, Electric
      Cooling
      • Central Air
      Appliances
      • Included: Cooktop, Dryer, Dishwasher, ENERGY STAR Qualified Dishwasher, ENERGY STAR Qualified Dryer, ENERGY STAR Qualified Freezer, ENERGY STAR Qualified Refrigerator, ENERGY STAR Qualified Washer, Electric Cooktop, Electric Water Heater, Free-Standing Freezer, Microwave, Oven, Refrigerator, Water Heater, Wine Refrigerator, Washer
      • Laundry: Inside, Laundry Room, Laundry Tub, Sink
      Features
      • Dual Sinks, Entrance Foyer, Living/Dining Room, Walk-In Closet(s)
      • Flooring: Concrete, Laminate, Tile
      • Windows: Storm Window(s)
      • Has fireplace: No
      Interior area
      • Total structure area: 3,720
      • Total interior livable area: 2,255 sqft
      Video & virtual tour

      Property

      Parking
      • Total spaces: 8
      • Parking features: Attached Carport, Circular Driveway, Carport, Driveway
      • Carport spaces: 2
      • Uncovered spaces: 6
      • Details: CarportSpaces:2.00
      Accessibility
      • Accessibility features: None
      Features
      • Levels: One
      • Stories: 1
      • Patio & porch: Covered, Patio, Rooftop
      • Exterior features: Garden, Outdoor Living Area
      • Has private pool: Yes
      • Pool features: In Ground, Pool Equipment
      • Has view: Yes
      • View description: Bay, Intercoastal, Pool, Water
      • Has water view: Yes
      • Water view: Bay,Intercoastal,Water
      • Waterfront features: Bayfront, Intracoastal Access, Navigable Water, No Fixed Bridges, Ocean Access, Seawall
      • Frontage type: Waterfront
      • Frontage length: 100.00,100.00
      Lot
      • Size: 0.34 Acres
      • Features: 1/4 to 1/2 Acre Lot, Sprinklers Automatic, Sprinkler System
      Details
      • Parcel number: 2452050080070
      • Zoning: 2001
      • Special conditions: Standard

      Construction

      Type & style
      • Home type: SingleFamily
      • Property subtype: Single Family Residence
      Materials
      • Brick, Concrete
      • Roof: Shingle
      Condition
      • Resale,Updated/Remodeled
      • New construction: No
      • Year built: 1958

      Utilities & green energy

      • Sewer: Public Sewer
      • Water: Public
      • Utilities for property: Electricity Connected, Sewer Connected, Water Connected
      Green energy
      • Energy efficient items: HVAC, Appliances

      Community & HOA

      Community
      • Subdivision: MASHTA ISLAND
      HOA
      • Has HOA: No
      Location
      • Region: Key Biscayne

      Financial & listing details

      • Price per square foot: $8,204/sqft
      • Tax assessed value: $7,506,916
      • Annual tax amount: $112,485
      • Date on market: 7/30/2026
      • Cumulative days on market: 51 days
      • Listing terms: Cash,Conventional
      • Electric utility on property: Yes

        Estimated market value

        $16,585,700

        $15.76M - $17.41M

        Not available

        Price history

        DateEventPrice
        7/30/2026Listed for sale$18,500,000-21.3%$8,204/sqft
        Source: BeachesMLS #B26058354 Report a problem
        2/7/2026Listing removed$23,500,000$10,421/sqft
        Source: BeachesMLS #RX-11060323 Report a problem
        2/7/2025Listed for sale$23,500,000+176.5%$10,421/sqft
        Source: BeachesMLS #RX-11060323 Report a problem
        3/9/2022Sold$8,500,000$3,769/sqft
        Source: Public Record Report a problem

        Public tax history

        YearProperty taxesTax assessment
        2025$112,485 +2.4%$6,855,108 -0.9%
        2024$109,802 +6.7%$6,916,728 +8.6%
        2023$102,890 +23.2%$6,371,245 +39%
        2022$83,488 +13.6%$4,582,083 +4.2%
        2021$73,461 +1.1%$4,397,303 0%
        2020$72,644 -0.2%$4,397,371 0%
        2019$72,826 +3.4%$4,397,439 0%
        2018$70,437 $4,397,507 -10.5%
        2017$70,437 -18.5%$4,910,766 +10%
        2016$86,399 +4.7%$4,464,333 +10%
        2015$82,558 +9.6%$4,058,485 +10%
        2014$75,353 +33.3%$3,689,532 +10%
        2013$56,526 +0%$3,354,120 +6.6%
        2012$56,526 +12.7%$3,146,000 +10%
        2011$50,141 -1.9%$2,860,000 +5%
        2010$51,123 -22.8%$2,722,719 -26.5%
        2009$66,186 -3.7%$3,704,315 -5.8%
        2007$68,746 +37.9%$3,931,345
        2006$49,835 --
        2005$49,835 +46.9%--
        2004$33,931 +5.7%--
        2003$32,086 +34.5%--
        2002$23,849 -13.3%--
        2001$27,495 --
        Find assessor info on the county website

        Monthly payment

        Est. payment

        Payment breakdown

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        All calculations are estimates and provided by Zillow, Inc. for informational purposes only. Actual amounts may vary.
        HOA fees may include property taxes on listings classified as Co-Ops. Contact the listing agent and/or owner for fee details.
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        Climate risks

        Neighborhood: 33149

        Getting around

        8 / 100
        Car-Dependent
        36 / 100
        Somewhat Bikeable

        Nearby schools

        GreatSchools rating
        Schools provided by the listing agent
        • Elementary: Key Biscayne K-8
        • Middle: Ponce De Leon
        • High: Coral Gables

        Source: BeachesMLS. This data may not be complete. We recommend contacting the local school district to confirm school assignments for this home.

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