In a statement on Friday, Florida's Health Department said of the three cases, two "appear to be related", reports Efe news.
The authorities had confirmed five such cases last month which led to the Department to alert people on taking measures to protect themselves from the mosquitoes that transmit dengue.
Apart from Miami-Dade, the highly populated southern Florida, another locally transmitted case was found in the neighbouring Broward County. However, the status of those affected was not yet known.
The disease, according to the World Health Organization, affects 390 million people worldwide. The common symptoms of dengue are fever, rashes, muscular and joint pains.
Haemorrhagic dengue is the most severe and can be fatal.
According to the Florida Health Department, the dengue virus was eradicated in the US decades ago and the only cases to be recorded until 2009 were of the people who contracted the disease in countries where it was present.
However in 2019, an outbreak of local transmission was reported in Key West, in the Florida Keys, with 22 confirmed cases.
Some 60 cases were recorded in 2010 and since then isolated cases have been reported.