Gioacchini, 21, signed a two-and-a-half year deal, with a club option for 2025. A league source confirmed that Caen will receive a percentage of any future transfer.
"Niko is an exciting young player that has a great ability to break lines and has a keen eye for goal," said EVP of soccer operations and general manager Luiz Muzzi. "He's begun to work his way into the national team pool already and we look forward to him furthering his young career with us here in Orlando."
Gioacchini is the latest U.S. international to switch clubs in a bid to secure more playing time ahead of the 2022 World Cup, set to take place in November. Earlier this week defender Shaq Moore moved to Nashville SC.
"[Orlando is] a place where I felt at home. A club with a history of being very family-like and the fans...The fans, the stadium, it's a place where there's a lot of energy and that's for sure a part of the reason I decided to come," Gioacchini said. "[Playing in MLS is] one of the parts I'm most excited about. Coming home, that feeling of coming back to my home country and getting the experience to play against the rising MLS and being a part of it. That's a great feeling."
A native of Kansas City, Mo., Gioacchini started his professional career with Paris FC before moving to Caen in 2018, where he went on to score nine goals in 49 league and cup appearances with the first team.
He spent the previous season on loan with Montpelier in Ligue 1, but failed to score in 31 league and cup appearances with the first team. He scored four goals in three appearances with the club's second team.
At international level, Gioacchini has made eight appearances for the U.S., scoring three goals.