"The work is in progress. It is not complete. It is doubtful that it will be ready for the presidential visit this weekend," Palm Beach Mayor Gail Coniglio told a local daily.
The daily published photographs of the work site on the lawn of Mar-a-Lago, the President's residence in the wealthy enclave.
Once the helipad is completed and operational, Trump will be able to fly to his residence from West Palm Beach International Airport instead of being driven in a motorcade that causes traffic jams.
The helipad is a 20.3 cm thick, 15.2 metres long platform of steel-reinforced concrete set 91.5 metres from the residential buildings, architect Rick Gonzalez, who designed the project, said.
In January, Palm Beach's Landmarks Preservation Commission and the mayor's office authorised construction of the helipad despite complaints from some neighbors about the helicopter's noise disturbing life on the upscale island.
Trump's visits to Mar-a-Lago have also prompted complaints from another nearby airport, where operations must be suspended when the President is in Palm Beach, and from town finance officials about increased spending on additional security.
On Friday, Trump is scheduled to attend a meeting on school choice and education reform at a Catholic school in Orlando.
He is expected to travel to Palm Beach after the event in Orlando.
The lavish Mar-a-Lago, which Trump acquired for less than $8 million in 1985, was built by cereal heiress and socialite Marjorie Merriweather Post in the 1920s.