Stallworth, a 32-year-old free agent who most recently played for New England, and Soleil Guerrero, 27, were rushed to a hospital, The Miami Herald reported. Guerrero was more severely injured than Stallworth, who is expected to resume his football career, the newspaper said.
The balloon operator was not injured, the Herald said.
"Donte' is in good spirits, considering the pain, but his primary focus is on the well-being of Soleil," his attorney, Christopher Lyons, said.
The couple were on the balloon ride to celebrate Guerrero's birthday. Weather reportedly was good when the incident occurred about 10 a.m. EDT while the balloon was landing south of Miami-Dade County.
The National Transportation Safety Board was investigating, the Herald said.
The balloon ride was booked through Balloon Over Miami, run by Aaron Farber, 39, of West Kendall, the newspaper said. Farber, who the Herald said could not be reached for comment, describes himself on his website as "very skilled and experienced" with a "perfect safety record."
Drew Rosenhaus, Stallworth's agent, said the player "should be fine."
"It's not going to have a long-term effect on him," Rosenhaus said. "He'll be returning in a few weeks to regular football activities and we expect him to resume his NFL career."
In 2009, Stallworth hit and killed a 59-year-old pedestrian on Florida's MacArthur Causeway. Blood tests showed Stallworth had a blood-alcohol level of 0.126 and he pleaded guilty to DUI manslaughter.