The newly single Prince, who recently split from his girlfriend of two years Cressida Bonas, was seen celebrating the lead-up to Guy's wedding, which will take place on Saturday 3 May in Memphis, Tennessee.
Harry, Guy and about thirteen friends were spotted enjoying dinner at local hotspot Hakkasan on Miami Beach, according to Us Weekly. An insider revealed that the group ordered crispy duck salad, dim sum, Chilean sea bass, stir-fried Bahamian lobster and charcoal grilled silver cod.
Prince Harry pictured on a royal tour in 2012
The party carried on "until after close" with Harry and his friends enjoying cocktails, tea and coffee. Club manager Guy and his nearest and dearest then danced the night away at LIV nightclub, located close to the restaurant.
Following their stay in Miami, the wedding party will travel to Memphis for Guy's nuptials to his Holiday Inn heiress bride Lizzy Wilson. The three-day wedding celebrations will kick off on Friday with drinks at the Memphis Hunt and Polo Club.
The main ceremony will take place on Saturday, and see Harry and his older brother Prince William act as ushers on the day.
Lizzy Wilson and Guy Pelly will marry this weekend
While William's wife the Duchess of Cambridge, nee Kate Middleton, gets along well with Guy, insiders have said that the stunning royal will not make the trip stateside as she has just returned from a three-week royal tour of Australia and New Zealand.
"After Australia, Kate's happy to leave William and Harry to it and spend some time at home with George," a source told The Mirror. "She appreciates the media storm her attendance would cause. William and Harry also don't want the thing to turn into a circus."
Prince William will leave Duchess Kate at home as he attends the US wedding
Cressida, meanwhile, was originally believed to be on the guest list but following the dance graduate's split with Harry, this no longer seems to be the case. The 25-year-old and her prince are said to have "paused for a breather" as their relationship hit the rocks.
The unexpected break-up was "very much an amicable one," with Harry keen to let his ex-girlfriend get on and pursue her career out of the public spotlight.
Prince Harry and Cressida Bonas were together for two years
Back home, members of the royal family attended the funeral of Mark Shand, the Duchess of Cornwall's younger brother. Camilla was accompanied by her husband Prince Charles and was pictured wiping away tears as she laid her brother to rest.