The most expensive dirt in the group and a second-home and family-trust market. Bought for the island and the schools, not for a cap rate. There are 37 houses for sale today. We read the closings, house by house, and the rental rule, before anything here goes on a shortlist.
The market, not the pitch
Two sets of numbers, and the gap between them is the useful part. On the left, what sellers are asking today. On the right, what buyers actually paid over the last twelve months.
Source: MLS (Miami Realtors / Bridge), single-family houses in Key Biscayne, Miami-Dade County, read on 21 September 2026. Active: 37 listings, 0 of them at or under $700,000, ranging from $3,300,000 to $237,000,000. Closed: 39 sales in the twelve months to that date, at a median 93.3% of the last asking price, in a median 93 days. Closed leases are excluded.
The book on the market is priced above what has been closing, by roughly 33% on price per square foot. That is a mix effect as much as a discount: the large and the waterfront sit longer. It is also the reason we underwrite from closings, never from asking prices.
One market, several prices
No. Grouped by plat, the spread is real: BISCAYNE KEY ESTATES asks a median $5,539,000 ($1,546/sf); TROPICAL ISLE HOMES 4 asks a median $7,575,000 ($2,076/sf); CAPE FLORIDA SEC 3 asks a median $16,500,000 ($2,323/sf). Anyone quoting you a single average is averaging across all of them.
| Plat | For sale | Median ask | $/sf | Closed 12 mo | Median paid | $/sf paid |
|---|---|---|---|---|---|---|
| BISCAYNE KEY ESTATES | 8 | $5,539,000 | $1,546 | 10 | $3,487,500 | $1,280 |
| TROPICAL ISLE HOMES 4 | 6 | $7,575,000 | $2,076 | 10 | $5,242,500 | $1,755 |
| CAPE FLORIDA SEC 3 | 5 | $16,500,000 | $2,323 | 1 | · | · |
| TROPICAL ISLE HOMES 3 | 2 | · | · | 3 | · | · |
| MASHTA ISLAND | 2 | · | · | 2 | · | · |
| TROPICAL ISLE HOMES 1 | 2 | · | · | 2 | · | · |
Read on 21 September 2026. Active listings and the closings of the twelve months to that date, grouped by plat as the county recorded it; a median on fewer than 5 records is withheld. The median house that sold was 3,520 sf and built in 1960. 12 of the 37 active houses are on water.
Live MLS · refreshed nightly
Pulled from the MLS every night. Open one to see the full record, or ask us to model it.
Before we recommend anything
0 of the 37 houses on the market mention Airbnb or short-term rental use in their own MLS text. We have not read the vacation-rental ordinance of Key Biscayne yet, so this page makes no claim about short stays: it is a year-round market until the rule is read, dated and sourced. Here is what we read, on the property you are actually considering, before it goes on a shortlist.
Under Florida Statute 509.032(7)(b), a city may prohibit or limit vacation rentals only through rules adopted on or before 1 June 2011. Whether Key Biscayne has such a rule, and what it says, is read from its code with the ordinance number and its date. Until then, nothing here says yes or no.
Any stay of six months or less needs the state DBPR vacation-rental licence and carries the county tourist development tax on top of 6% Florida sales tax and the county surtax, whatever the city says.
What we read parcel by parcel is the record at the county and at the city, the flood zone and the roof age, and we note where we read it and on what date.
A homeowners association or a deed restriction can forbid what a city allows. On a house this is often the binding constraint.
What this means for an investor: underwrite this zone on annual leases and on resale, which is what the closings and the signed leases measure; a short-stay upside, if the ordinance allows one, is a bonus to verify, never the base case.
Florida Statutes 509.032(7)(b), 2025 text. The city ordinance has not been read for this page; when it is, its number, date and reader will appear here. Nothing on this page certifies that a rental is legal at any address, and no number here is a projection of what a house will earn.
Same coast, other rules
Other house neighborhoods a few minutes away, each with its own price and its own rental rule. The question that decides between them is answered on its own page.
Asked before every shortlist
We have not read the Key Biscayne ordinance yet, so this page does not say. Under Florida Statute 509.032(7)(b) a city may only prohibit or limit vacation rentals through rules adopted on or before 1 June 2011; the answer is the ordinance number and its date, which we read before any shortlist. Any stay of six months or less needs the state DBPR licence and carries the tourist tax regardless.
37 are for sale on 21 September 2026, at a median asking price of $7,490,000 and $1,988 per square foot, from $3,300,000 to $237,000,000. Over the previous twelve months 39 sold, at a median $4,600,000 and $1,498 per square foot, in a median 93 days and at 93.3% of the last asking price.
35 single-family houses were leased through the MLS in the twelve months to 21 September 2026, at a median $21,500 a month and $6.32 per square foot. Against the median house sold in the same period that is a 5.6% gross yield before property tax, insurance, upkeep and vacancy, and it is a long-lease number, not a short-stay projection.
No. Grouped by plat, the spread is real: BISCAYNE KEY ESTATES asks a median $5,539,000 ($1,546/sf); TROPICAL ISLE HOMES 4 asks a median $7,575,000 ($2,076/sf); CAPE FLORIDA SEC 3 asks a median $16,500,000 ($2,323/sf). Anyone quoting you a single average is averaging across all of them.
One email a week: what closed, what is new, one measured opinion. No listings dump.
The 12-month report · 24h
The closings of the last twelve months, the rents signed, and the rental rule with its source: the report behind the numbers on this page, plus a shortlist if you tell us the budget and what the house has to do.
What you get: the 12-month report on Key Biscayne · a shortlist from the MLS and off-market · the parcel-level rental read, with its source and its date.
Send us the address. We come back with the closed comparables on its own street, the rents signed nearby and what the record says about rental use on that parcel.