The Republican senator was notified of the accident while coming off stage after a rally with GOP presidential candidate Mitt Romney Saturday afternoon.
The senator campaigned with Romney at two Florida rallies on Saturday and was scheduled to attend a third before being picked up by a state police cruiser along Romney's motorcade route.
Rubio spokesman Alex Conant wrote in an email late Saturday that Amanda, who is the senator's oldest daughter, was in "fair condition" after the afternoon accident.
"While visiting with classmates, she was a passenger on a golf cart involved in a collision in a private gated community," Conant wrote. "She was airlifted to Miami Children's Hospital with a head injury. She has been admitted to the Pediatric Intensive Care Unit."
"Senator and Mrs. Rubio are grateful for all the outpouring of support and prayers," he added, including calls from President Barack Obama and Vice President Joe Biden and a personal message from Romney.
According to The Miami Herald, a Romney spokeswoman said, "Governor Romney spoke with Senator Rubio and expressed his concern and hope for Amanda Rubio's quick recovery."
Miami-Dade County Commissioner Rebeca Sosa, a family friend, said outside the hospital that Amanda "had a concussion" but was doing better, according to a video posted on The Herald's website.
"He is with her," Sosa said. "The family's next to her and he's already in the hospital.
According to the newspaper, Rubio has four children. He kept his family in his hometown after being elected to the U.S. Senate, preferring to commute to Washington from his West Miami home.